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UNIVERSITY  OF  CALIFORNIA. 


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STEAM    PIPES 


STEAM     PIPES 

THEIR     DESIGN     AND 
CONSTRUCTION 

A  Treatise  of  the  Principles  of  Steam  Convey- 
ance and  Means  and  Materials  Employed 
in  Practice,  to  Secure  Economy 
Efficiency  and  Safety 


By 
WM.    H.    BOOTH 

AUTHOR    OF    "  LIQUID    FUEL    AND    ITS    COMBUSTION*' 

Member  of  the  American  Society  of  Civil  Engineers  ;    late  of  the 

Manchester  Steam    Users'  Association,    The   Neiv  South   Wales   Government 

Railway  Def>t.t  etc. 


SECOND  IMPRESSION 


LONDON 

ARCHIBALD  CONSTABLE  &  CO  LTD 

1906 


1 


BUTLER  &  TANNER, 
THE  SELWOOD  PRINTING  WORKS. 

FROME,  AND  LONDON. 


OF   THE 

UNIVERSITY 

OF 


PREFACE 

IF  any  engineer  will  refer  to  his  various  text-books 
for  information  on  steam  piping,  he  will  find 
very  little  to  assist  him.  The  earliest  steam  pipes 
served  to  convey  steam  at  atmospheric  pressure 
into  cylinders  of  large  size.  The  object  of  the  steam 
was  simply  to  fill  the  cylinder  with  a  condensible 
vapour,  so  that  upon  cooling  it  there  was  a  vacuum 
formed  and  the  air  pressure  on  the  opposite  face 
of  the  piston  was  made  to  do  work.  So  long  as 
the  piston  could  be  drawn  up  by  the  weight  of  the 
pump  spear  rods  hung  to  the  opposite  end  of  the 
beam,  it  mattered  little  that  the  pipes  were  small, 
for  there  was  no  object  in  filling  the  cylinder  with 
steam  at  full  boiler  pressure,  for  the  vacuum  ob- 
tained on  condensing  would  be  better  as  the  steam 
was  the  less  in  quantity.  When  the  steam  engine 
was  made  rotative  its  piston  speed  became  great 
and  more  regular,  and  pipes  of  a  definite  size  began 
to  be  found  necessary.  Most  of  the  early  books 
on  the  steam  engine  gave  engine  proportions  of  a 
very  empirical  order,  deducing  them  from  the 
cylinder  diameter  by  formulae  that  were  sound  only 
so  far  as  they  were  applied  to  engines  constructed 


201593 


PREFACE 

to  standard  practice.  Standard  practice  in  so  far 
as  beam  engines  were  concerned  was  very  much  as 
Boulton  and  Watt  had  made  it,  and  no  doubt  the 
proportions  given  by  these  curious  old  formulae 
were  properly  deduced  from  what  experience  had 
fixed  upon  as  good  practice.  Our  modern  practice 
in  steam  pipes  is  thus  the  outgrowth  of  Boulton 
and  Watts'  early  experience.  It  is  a  well-known 
fact  that  when  steam  escapes  to  atmosphere  through 
an  opening,  the  weight  of  flow  is  proportionate 
approximately  to  the  absolute  pressure.  Thus 
steam  at  ninety  pounds  absolute  pressure  will  escape 
three  times  as  fast  as  regards  weight  as  will  steam 
of  thirty  pounds  absolute  pressure.  Yet  as  steam 
pressures  have  advanced  the  area  of  pipes  has  not 
diminished  accordingly.  Any  steam  boiler,  no 
matter  at  what  pressure  it  may  be  worked,  will  con- 
vert a  steady  weight  of  water  into  steam.  It  follows 
therefore  that  for  boilers  of  high  pressure  the  steam 
pipes  may  be  proportionately  less  than  for  low 
pressures.  But  as  all  practice  has  been  towards 
higher  pressures,  it  has  always  been  the  case  that 
steam  pipe  mounting  blocks,  steam  entrance  pipes 
to  engines,  steam  valves  for  any  stated  size  of  boiler, 
'have  been  gauged  by  last  year's  practice  rather 
than  this  year's,  and,  as  is  always  the  case  in  en- 
gineering practice,  there  has  been  a  delay  in  cutting 
down  pipe  dimensions  to  the  equivalent  of  the  rise 
in  pressure.  While  steam  pipes  may  be  too  small 
they  are  probably  more  often  too  large,  and  not 
the  less  so  that  they  have  been  called  frequently 

vi 


PREFACE 

to  supply  many  engines  of  high  rotative  speed  which 
make  a  demand  on  the  steam  supply  that  is  prac- 
tically continuous.  Apart  from  mere  sufficiency 
of  piping,  as  such,  there  are  the  numerous  details 
involved  in  flange  diameters,  bolts,  centre  lines, 
sockets,  joints,  and,  not  less  important,  valves, 
which  all  demand  investigation.  It  is  the  object 
of  this  book  to  bring  together  such  information  as 
may  be  useful  in  connection  with  steam  pipes  as 
will  be  of  assistance  to  the  engineer  who  has  to  face 
problems  of  this  sort.  Steam  piping  to-day  is  so 
costly  an  item,  especially  when  large  valves  are 
employed,  that  every  effort  should  be  made  to  mini- 
mize such  cost  without  sacrifice  of  efficiency.  No 
attempt  has  been  made  to  put  together  everything 
that  is  published  on  steam  piping.  Selections  only 
have  been  possible,  and  the  author  is  indebted  among 
others  to  the  Babcock  &  Wilcox  Co.  for  permission 
to  reproduce  from  their  book  Steam  and  other  of 
their  pamphlets  ;  to  Mr.  A.  J.  Lawson,  of  the  British 
Electric  Traction  Co. ;  the  Mannesmann  Tube  Co. ; 
the  Cruse  Superheater  Co. ;  and  to  Mr.  Arthur 
Venning  ;  also  to  Messrs.  Holden  &  Brooke ;  Messrs. 
Templer  &  Ranoe,  whose  productions  the  author 
has  employed  to  illustrate  the  book ;  Messrs.  Yates 
&  Thorn,  for  numerous  illustrations  of  Lancashire 
practice  ;  Mr.  Stromeyer,  of  the  Manchester 
Steam  Users'  Association  ;  Messrs.  J.  E.  &  S.  Spencer, 
Ltd. ;  Mr.  Thos.  Walker,  of  Tewkesbury,  and  others. 
In  the  book  will  be  found  various  tables  of  dimen- 
sions of  junction  pieces,  valves  and  flanges.  In 

vii 


PREFACE 

printing  these  the  author  has  merely  been  influenced 
by  a  desire  to  put  before  readers  a  few  examples 
as  a  guide,  and  not  as  a  fixed  and  determined 
standard.  There  are  many  so-called  standards 
which  differ  from  one  another  in  but  little,  and  per- 
haps the  most  important  detail  to  standardize  is  the 
flange  as  regards  diameter,  bolt  circle  and  bolt 
numbers,  and  their  relation  to  centrelines.  A  com- 
mittee is  now  sitting  on  this  subject,  and  doubtless 
will  arrive  at  a  result  which  engineers  can  accept. 
It  will  probably  be  useful  as  a  guide  to  have  general 
dimensions  of  even  a  single  make  of  valve,  but  the 
author  would  suggest  that  overall  dimensions  of 
valve  bodies  ought  also  to  be  made  standard,  for 
such  would  make  it  possible  to  get  out  a  whole 
system  of  pipes  before  deciding  on  where  the  valves 
should  be  obtained. 

There  are  so  few  and  so  small  differences  between 
one  maker's  products  and  those  of  another  that  a 
universal  standard  should  be  quite  practicable. 

2,  QUEEN  ANNE'S  GATE, 
WESTMINSTER. 


vm 


TABLE   OF   CONTENTS 

CHAP.  PAGE 

I    THE  DUTY  AND  OBJECT  OF  PIPES — FAULTS  OF 

DUPLICATE  PIPE  SYSTEMS  i 

II    FLOW  OF  STEAM— Loss  OF  HEAD — VELOCITY — 
FORMULA — TABLES— EQUATION     OF    PIPES — 
RESISTANCE  OF  ELBOWS,  ETC.        ...        4 

III  MATERIALS— COPPER,      CAST      IRON,      STEEL — 

THICKNESS  OF  PIPES — JUNCTION  PIECES-- 
DIMENSIONS —  FLEXIBLE  PIPES  —  RIVETED 
PIPE— FLANGES— JOINTS — SOCKETED  PIPES— 
WHITWORTH  PIPE  THREADS— AMERICAN  PIPE 
THREADS 23 

IV  EXPANSION  — COEFFICIENTS  —  SPRING     BENDS — 

GENERAL  ARRANGEMENT — SLIDING  JOINTS — 
SWIVEL  JOINT  —  ANCHORING  —  TEMPERATURE 

AND  PRESSURE  OF  STEAM  55 

ix 


CONTENTS 

CHAP.  PAGE 

V    STRENGTH  OF  PIPES— THREADS— BOARD  OF  TRADE 

RULES          .        .        .        .-•.'..        .72 


VI  ANTI-PRIMING  PIPES—OUTLET  VALVES— DRAIN 
PIPES  —  INCLINATION  —  ISOLATING  VALVES — 
WATER  HAMMER— BRANCHES  .  ..  .76 

VII  PIPE  JOINTS — SPIGOT — SOCKET — SCREW — FLANGES 

—  JOINTING      RINGS,      ETC.  —  SUPERHEATED 
STEAM 83 

VIII  PIPE  SUPPORTS— BRACKET  SUSPENSION— PILLARS 

—  PLAIN     BRACKETS  —  VIBRATION  —  ANCHOR 
BRACKET— TABLES  OF  DIMENSIONS        .         .      88 

IX  ERECTION  OF  PIPES— TEMPLETS  FOR  PIPES — 
TAPER  JOINT  RINGS— EXTENSIONS  TO  EXISTING 
PIPES — PIPE  BENDING  ....  97 

X  GENERAL  ARRANGEMENTS — RELATIVE  PostriON 
OF  BOILERS,  ENGINES  AND  SUPERHEATERS- 
SIZE  OF  VALVES — BOILER  OUTPUT — MODERN 

BOILER  CAPACITY 105 

x 


CONTENTS 

CHAP.  PAGE 

XI  VALVES,  GLOBE,  ANGLE,  FULLWAY  OR  GATE — 
BYE-PASS  RELIEF — REVERSED  FLEXIBLE  SEATS 
— ISOLATION — MATERIALS  ....  112 

XII    DRAINAGE — STEAM  TRAPS         ....     128 

XIII  J  UNCTION  PIECES  AND  FLANGES — WEIGHTS — CON- 

STRUCTION— MATERIALS — FLANGE  DIMENSIONS 

— BOLT  PITCH — STANDARDS  .         .         .         .133 

XIV  SEPARATORS  —  EXHAUST  HEADS  —  ATMOSPHERIC 

VALVES         . 145 

XV  SUPERHEATED  STEAM,  RELATIVE  VOLUMES — 
PIPE  COVERINGS — NORTON'S  EXPERIMENTS — 
ATKINSON'S  REPORTS  .....  152 

XVI    WEIGHTS     OF     PIPE — SPECIFIC     GRAVITY     OF 

MATERIALS 173 

XVII    THE  KINETIC  THEORY  OF  GASES  IN  RELATION 

TO    THE    FLOW   OF   STEAM        .  r  «  .178 


XI 


CHAPTER    I 

Steam  Pipes :   Their   Duty  and   Object 
HE  object  of  a  steam  pipe  is  to  convey  steam 


T 


from  point  to  point. 

A  steam  pipe  as  ordinarily  understood  is  for  the 
conveyance  of  steam  from  the  boiler  to  the  engine,, 
or  to  other  apparatus,  such  as  a  dye  vat  or  brewing 
copper,  etc. 

In  the  early  days  of  steam  engineering  there  were 
no  steam  pipes  ;  the  working  cylinder  of  the  engine 
was  wholly  or  partially  connected  to  the  boiler  or 
joined  by  a  narrow  neck,  which,  becoming  gradually 
longer,  developed  into  a  pipe.  Sometimes  of  rect- 
angular section  for  convenience  under  special  cir- 
cumstances, the  natural  and  usual  cross-section  of 
a  pipe  is  the  circle,  that  being  a  figure  which  con- 
tains a  maximum  of  area  within  a  minimum  cir- 
cumscribing boundary,  and  also  being  the  only  figure 
of  maximum  strength  to  resist  bursting,  and  there- 
fore requiring  no  internal  or  other  stays. 

Since  a  steam  engine  gives  the  best  results  at  the 
highest  pressures,  the  duty  of  a  steam  pipe  is  to  con- 
vey steam  to  the  engine  with  a  minimum  of  loss  of 
pressure.  Steam  being  hotter  than  the  air  surround- 
ing the  pipes  must  lose  some  of  its  heat  in  its  passage 

I  B 


STEAM    PIPES 

through  pipes.  Obviously,  therefore,  pipes  must 
be  of  minimum  size.  This  is  inconsistent  with  a 
minimum  pressure  loss,  and  a  compromise  must 
therefore  be  come  to  between  loss  of  heat  and  loss 
of  pressure.  If  that  compromise  could  be  worked 
out,  it  would  be  found  by  equating  the  loss  of  coal 
due  to  loss  of  economy  consequent  on  loss  of  a  given 
amount  of  pressure,  and  the  loss  by  radiation  of 
heat  that  would  be  incurred  by  making  the  pipe 
large  enough  to  prevent  said  loss  of  pressure. 

Beyond  a  certain  small  loss  of  pressure,  any 
further  increase  of  pipe  diameter  affords  so  little 
further  reduction  of  friction  and  adds  so  much  to 
the  heat  radiation  losses  from  the  pipe  surface  that 
very  large  pipes  must  not  be  used,  for  they  involve 
also  increased  capital  expenditure  in  pipe  sizes, 
coverings,  flanges  and  valves  out  of  all  proportion 
to  the  small  gain  of  pressure. 

The  broad  principles  to  be  observed  to  enable  a 
pipe  to  perform  a  maximum  duty  are  that  it  shall 
take  as  direct  a  course  as  practicable  between  any 
two  points,  shall  be  as  smooth  internally  as  it  can 
reasonably  be  made,  and  shall  have  bends  of  large 
radius.  All  these  points  are  compelled  to  be  neg- 
lected by  circumstances,  but  they  afford  a  basis  for 
design. 

As  a  steam  pipe  is  meant  to  convey  steam  and 
will  be  called  on  to  convey  as  much  water  as  may 
be  formed  in  it  by  condensation  due  to  cooling,  this 
must  be  provided  against  by  suitably  covering  the 
pipes  with  a  non-heat  conducting  substance.  Other- 

2 


THEIR  DUTY  AND  OBJECT     f 

wise  not  only  is  heat  lost,  but,  water  being  formed, 
must  be  impelled  along  the  pipe  at  the  expense  of 
the  steam,  which  will  lose  pressure  as  a  result. 

As  a  steam  pipe  failure  will  cause  the  stoppage 
of  a  whole  power  station,  the  practice  has  grown 
up  among  electrical  engineers  of  duplicating  the 
steam  pipes.  Hence  arose  that  nuisance  the  ring 
main,  with  its  myriad  of  costly  valves,  its  maximum 
of  condensation  and  its  minimum  of  safety.  The 
ring  main  ought  only  to  be  employed  where  other 
conditions  render  it  obligatory,  and  these  only  occur 
as  a  rule  with  initially  bad  designs.  The  ring  main 
is  not  a  steam  engineer's  device.  Steam  engineers 
have  always  arrived  at  directness  of  pipes  knowing 
the  losses  of  heat  in  long  pipes,  and  they  insist  on 
the  use  of  the  best  materials  so  as  to  minimize  the 
chance  of  failure  rather  than  countenance  the  dupli- 
cation of  bad  work  which  has  arisen  from  want  of 
knowledge  of  steam  engineering  conditions  and  an 
apparently  foregone  conclusion  that  break-downs 
are  necessary,  and  must  be  encouraged  to  occur  by 
provision  of  a  maximum  of  parts  to  fail. 


CHAPTER    II 
The   Flow   of  Steam 

RANKINE,  in  his  work  on  the  Steam  Engine, 
gives  the  following  formula  for  the  velocity 
of  flow  of  steam  where  — 

V  =  velocity  in  feet  per  second. 
g    =  gravity  =  32-2. 

7    =  1-3- 

po   =  ideal  pressure  at  32°  F. 

To  =  absolute  temp,  at  32°  F. 
Ti  =          „          „        at  pressure  pt. 
T*  =          „          „          „        „       p2. 
pi    =          „       pressure  in  boiler. 
p2  =          „          „          at  steam  chest. 
v0    =  volume  ideal  at  32°. 
po  v0  =  42141. 

k    =  coefficient  of  contraction. 

Vi    =  volume  of  i  pound  of  steam  at  pi. 


Substituting  values  this  becomes  — 


=     /J64>4  x  i>3  x  42141  X 

V   \  493.  x  0-3 

=  ^71066  =  265 

feet  per  second,  where  pi  =  200   Ib.   absolute  and 

4 


THE  PLOW  OF  STEAM 

p2  =  197  lb.  That  is  to  say,  with  a  drop  of  pres- 
sure of  3  pounds  the  velocity  in  a  short  straight 
pipe  may  be  265  feet  per  second. 

For  small  differences  of   pressure  Rankine  gives 
an  approximate  formula  — 


/2g°x  42141-  rifri-fr)     (6) 

'V 


Substituting  values  gives  F  =  ^72260  =  270  feet 
per  second,  which  is  not  a  serious  difference  from 
the  complicated  formula. 

In  his  Rules  and  Tables,  Rankine  gives  a  rough 
approximation  of  the  weight  of  steam  flow  per  second 
where  the  initial  and  final  pressures  are  p±  and  p2 
respectively,  and  q  =  pounds  per  second  per  unit 
of  area. 

(1)  Where  p2  =  or  <  5  p±  •  q  =  pt  4.  70  nearly. 

o 
This  formula  is  only  useful  when    the    external 

or  final  pressure  is  low. 

(2)  Where  p,  >3.#1,  q  =  £ 


Applying  this  formula  (2)  to  the  case  of  steam  of 
200  lb.  (28,800  lb.  per  square  foot)  flowing  with  a 
loss  of  3  lb.,  or  to  a  final  pressure  of  197  lb.  (28,368 
lb.  per  square  foot),  we  have  by  (2)  — 

' 


or  675-4  x  0-1511  =  102-06  pounds. 
As  at  197  pounds  pressure  there  are  2-26  cubic 
feet  per  pound,  the  velocity  of  flow  per  second  will 

5 


STEAM    PIPES 

be  2-26  x  102  =  230-6  feet,  which  again  is  not  very 
seriously  different  from  the  velocities  found  by 
the  more  strict  formulae. 

Ordinarily  gases  flow  by  virtue  of  the  same  rules 
as  apply  with  liquids.  The  rule  for  the  flow  of  a 
liquid  is  v  =  x/2p  or  v  =  8  </h  (3),  where  h  is  the 
head  in  feet.  For  gases  h  is  that  height  of  a 
column  of  gas  equivalent  to  the  pressure.  Then 
in  the  case  in  point  of  steam  flowing  from  200  Ib. 
to  a  pressure  of  197  Ib.,  the  pressure  difference  per 
square  foot  is  432  Ib.  and  the  mean  density  is 
2*275  cubic  feet  per  pound,  whence  the  virtual 
head  in  feet  is  h  =  432  x  2-275  =  982-8  feet. 

Then  v  =  8  ^982-8  =  252  feet  per  second. 

It  is  obvious,  therefore,  that  so  far  as  regards 
steam  velocity  in  ordinary  practice  no  specially 
accurate  formula  is  needed.  Had  the  pressure 
difference  been  only  one  pound  per  square  inch  or 
144  pounds  per  square  foot,  the  velocity  would  have 

been  v  =  8  \/ ,  or  144-8  feet  per  second. 

In  Spon's  Dictionary  of  Engineering  the  following 
metrical  formula  is  given — 

v  =  V  2  g  (P  —  p}  -.  where    (4) 
d 

v  is  the  velocity  in  metres  per  second. 

g°  =  gravity  =  9-8088  metres  per  second. 

P  and  p  =  initial  and  final  pressures  in   metres 

of  mercury  column. 
<P  —  Sp.  gr.  of  mercury. 
d   =  „     „     „     steam. 

6 


THE    FLOW    OF    STEAM 

This  formula  reduces  to  v  =   \/2O2'74(P-p\ 

a 

when  P  and  p  are  the   pressures  stated   in  atmo- 
spheres. 

Our  standard  example  works  out  as  P  —  p  = 
0*203,  and  v  =  ^5837  =  76-00  metres,  or  249  feet 
per  second  as  found  by  the  previous  rule. 

The  calculated  velocities  above  found  cannot  be  em- 
ployed in  practice,  because  they  are  reduced  by  fric- 
tion and  by  condensation  which  produces  friction. 

This  is  one  reason  why  superheated  steam  travels 
so  much  better  than  wet  steam.  The  velocity  to 
be  counted  upon  must  therefore  be  reduced  in  accord- 
ance with  the  length  of  pipe,  its  bends  and  other 
resistances. 

D'Aubisson  found  that  resistance  is  directly  pro- 
portional to  length,  that  it  increases  with  the  square 
of  the  velocity,  and  it  is  inversely  as  the  diameter. 

He  applied  a  correction  to  the  velocity  found  by 

the  metrical  formula  (4)  namely,  V _ 

where  D  and  L  are  the  diameter  and  the  length  of 
the  pipe  in  metres.  D'Aubisson's  experiments 
were  made  with  air  in  tin  pipes,  and  the  formula 
will  be  the  more  correct  as  the  pipes  are  smoother. 
Probably  for  cast-iron  pipes  the  reduction  of  flow 
will  exceed  that  given  in  the  formula  worked  out 
for  a  pipe  30  metres  long  and  0-25  diameter,  which 
corresponds  with  a  pipe  about  100  feet  by  10  inches 

diameter ;  the  result  is  y  °*25    or  practically  the 

0-964 

7 


STEAM    PIPES 

velocity  is  reduced  to  one  half,  showing  that  friction 
is  very  considerable. 

It  is  usual  in  practice  to  require  to  know  the  dia- 
meter where  the  quantity  and  the  fall  of  pressure 
are  given  as  in  fixing  the  pipe  diameter  for  a  boiler 
of  a  given  evaporative  capacity  at  a  certain  dis- 
tance from  the  boiler. 

Calling  Q  the  volume  in  cubic  metres  per  second. 
L  =  pipe  length  in  metres. 
D  =  pipe  diameter  in  metres. 
P  =  difference   of   pressure   available    in 

metres  of  mercury. 
d   =  density  of  gas  relative  to  water. 
Then  D  =  -36  A/(Q'Q238  L  +  D)  x  Q2  d     ; 

This  formula  may  first  be  worked  out  with  an 
assumed  value  for  the  D  under  the  root  sign.  It 
may  be  taken  conveniently  as  that  diameter  which 
will  require  a  flow  of  30  metres  per  second.  This 
assumed  value  is  then  used  under  the  root  sign  and 
the  formula  worked  out.  If  the  calculated  and  the 
assumed  values  of  D  are  found  to  differ,  the  new 
value  of  D  as  calculated  can  now  be  used  under 
the  root  sign  and  a  fresh  value  calculated  which 
will  be  very  close  to  the  first  calculated  value  where 
pipes  are  of  usual  lengths  or  several  diameters  long. 
For  convenience  in  using  these  metrical  formulae 
the  following  equivalents  will  be  useful  in  reducing 
British  data  to  metrical— 

i  metre  =  39-37  inches  =  3-28  feet. 

i  foot  =  0*305  metre. 

8 


THE    FLOW    OF    STEAM 

i  inch  =  0-0254  metre 

i  cubic  foot   =  0-0283  cubic  metre, 
i      „    metre  =  35-316  cubic  feet, 
i  pound  per  square  inch  difference  of  pressure 
=  0-052  metre  of  mercury  column. 
A  formula  sometimes  employed  for  the  velocity 

of  flow  in  a  pipe  is  V  =  Soy.        ;  the  value  of 

JL/ 

H  being  v.p.  144,  where  V  =  feet  per  second,  v  the 
volume  in  cubic  feet  of  i  pound  of  steam  at  the 
initial  pressure,  L  and  D  the  length  and  diameter 
of  the  Dine  in  feet,  a.nH  -/>  the 


Page  8,  line  14  for 
Then  £>=  -36 

jr 

read 

ThenZ)=  .36  A/(°'*g38  LlTD)^"^ 
,,__-_^  __^    .  5Q 

per  second,  and  Va  =  278  x  0-196  =  54-5  cubic 
feet  of  flow  per  second. 

Hutton  gives  a  rule  for  the  outflow  of  steam  into 
an  external  pressure  not  more  than  58  per  cent,  of 
the  internal  pressure,  as  follows  : — 

W  =  weight  of  steam  discharged  per  minute. 

Then  W=  —^-y  where 

P  =  absolute  pressure  in  pounds  per  square  inch. 
A  =  area  of  pipe  in  square  inches. 
C  —  1-38  for  pipes  up  to  10  ft.  long. 

9 


STEAM    PIPES 

velocity  is  reduced  to  one  half,  showing  that  friction 
is  very  considerable. 

It  is  usual  in  practice  to  require  to  know  the  dia- 
meter where  the  quantity  and  the  fall  of  pressure 
are  given  as  in  fixing  the  pipe  diameter  for  a  boiler 
of  a  given  evaporative  capacity  at  a  certain  dis- 
tance from  the  boiler. 

Calling  Q  the  volume  in  cubic  metres  per  second. 

L  =  pipe  length  in  metres. 

D  =  pipe  diameter  in  metres. 

P  =  difference   of   pressure   available   in 


assumed  value  is  then  used  under  the  root  sign  and 
the  formula  worked  out.  If  the  calculated  and  the 
assumed  values  of  D  are  found  to  differ,  the  new 
value  of  D  as  calculated  can  now  be  used  under 
the  root  sign  and  a  fresh  value  calculated  which 
will  be  very  close  to  the  first  calculated  value  where 
pipes  are  of  usual  lengths  or  several  diameters  long. 
For  convenience  in  using  these  metrical  formulae 
the  following  equivalents  will  be  useful  in  reducing 
British  data  to  metrical — 

i  metre  =  39-37  inches  =  3-28  feet. 

i  foot  =  0*305  metre. 

8 


THE    FLOW    OF    STEAM 

i  inch  =  0-0254  metre 

i  cubic  foot   =  0-0283  cubic  metre, 
i      „    metre  =  35-316  cubic  feet, 
i  pound  per  square  inch  difference  of  pressure 
=  0-052  metre  of  mercury  column. 
A  formula  sometimes  employed  for  the  velocity 

of  flow  in  a  pipe  is  V  =  50  V          ;  the  value  of 

JL/ 

H  being  v.p.  144,  where  V  =  feet  per  second,  v  the 
volume  in  cubic  feet  of  i  pound  of  steam  at  the 
initial  pressure,  L  and  D  the  length  and  diameter 
of  the  pipe  in  feet,  and  p  the  difference  of  pressure 
between  the  two  ends  of  the  pipe.  The  number  of 
cubic  feet  per  second  is  then  Va,  where  a  is  the  pipe 
area  in  square  feet.  Thus  for  a  6-inch  pipe  50  feet 
long,  carrying  steam  of  100  pounds  absolute  pres- 
sure, with  a  drop  of  5  pounds,  we  have  v  =4-29 
from  any  steam  table,  whence  H  =  4-29  x  5  x  144  = 

3088-8.     Hence,  V  =  5oA/3°88>8  x  °'5=  278  feet 

50 
per    second,    and    Va  =  278  x  0-196  =  54-5   cubic 

feet  of  flow  per  second. 

Hutton  gives  a  rule  for  the  outflow  of  steam  into 
an  external  pressure  not  more  than  58  per  cent,  of 
the  internal  pressure,  as  follows  : — 

W  =  weight  of  steam  discharged  per  minute. 

Then  W=  ^4,  where 
O 

P  =  absolute  pressure  in  pounds  per  square  inch. 
A  =  area  of  pipe  in  square  inches. 
C  —  1-38  for  pipes  up  to  10  ft.  long. 

9 


STEAM    PIPES 

=  i'39  for   pipes  up    to  40  feet  long. 
=  *'42     »      >>        >>    „    7°    »       » 

=   1'45       »          »  y,       )>    IO°       >y  » 

P  of  course  must  not  be  less  than  12  pounds 
above  the  atmosphere. 

The  velocity  of  flow  through  a  valve  or  short  pipe 
is  V  =  32  J  T  +  460,  when  T  is  the  temperature 
and  V  =  feet  per  second. 

Neither  of  these  rules  bears  upon  boiler  steam  pipes, 
because  a  drop  of  42  per  cent,  or  more  could  not  be 
tolerated.  The  rules  are  useful  for  special  cases. 

PRACTICAL  RULES. 

Hutton  gives  as  a  good  practical  rule  that  in  ordin- 
ary cases  steam  velocity  should  not  exceed  85  feet 
per  second  =  5,ioo  feet  per  minute.  If  very  short 
and  straight  the  velocity  may  be  no  feet.  He 
supposes  steam  to  follow  the  piston  for  full  stroke, 
and  gives  the  following  rule  for  steam  pipe  area — 

Cylinder  Area  x  Piston  Speed  per  minute 

~5i55~  =Pipearea. 

This  rule  is  purely  empirical,  for  it  supposes  con- 
tinuous steaming  and  neglects  the  higher  piston 
velocity  at  middle  stroke. 

Referred  to  evaporation  the  steam  pipe  area  is 
given  as — 

Pounds  of  Steam  per  minute  x  volume  of  steam 
relative  to  water 

A    —  t 

Velocity  in  feet  per  minute  x  62-42  -f- 144. 
Mr.  Stromeyer,  of  the  Manchester  Steam  Users' 
Association,  gives  as  a  rough  rule  for  sectional  area 
of  steam  pipes  in  square  inches  =  A. 

10 


A  = 


THE    FLOW    OF    STEAM 
180  x  Sum  of  widths  of  furnaces  in  inches 


Absolute  Pressure. 

This  rule  corresponds  with  a  velocity  of  8,000 
feet  per  minute  and  a  fuel  consumption  at  the  rate 
of  25  pounds  per  square  foot  per  hour  on  grates 
6  feet  long.  Obviously  the  rule  has  been  empiricised 
from  ordinary  rates  of  evaporation  and  combustion. 

In  ordinary  land  practice  the  constant  becomes 
240,  but  where  there  is  an  ample  excess  of  boiler 
pressure,  as  in  case  of  Belleville  boilers,  for  example, 
which  carry  pressures  much  in  excess  of  what  is 
permitted  to  reach  the  engines,  the  constant  need 
not  be  more  than  120. 

The  combined  formula  for  flow  of  steam  due  to  differ- 
ence of  pressure  and  length  of  pipe  and  diameter  is — 

where    (i) 

W  =  the  weight  in  pounds  per  minute. 

D  =  the  weight  per  cubic  foot  of  steam  at  the 
pressure. 

pi  and  p2  =  the  initial  and  final  pressures. 

L  =  the  pipe  length  in  feet. 

d  =  the  pipe  diameter  in  inches. 

Table  i  has  been  calculated  for  Steam  (B.  &  W. 
Boiler  Co.)  from  this  formula  for  pipes  having  a 
length  of  240  diameters,  straight  and  smooth.  The 
results  are  in  pounds  per  minute.  In  using  this 
formula  it  must  be  noted  that  actual  pipe  diameters 
are  employed  as  per  Table  II.,  which  gives  the  pipe 
diameters  on  which  the  Table  I.  is  calculated  for  all 
sizes  below  six  inches. 

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STEAM    PIPES 


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12 


THE    FLOW    OF    STEAM      « 


In  order  to  render  the  table  suitable  for  pipes 
with  bends  and  valves,  the  values  of  these  are  as 
follows. 

The  resistance  of  the  first  opening  from  the  boiler 
and  that  of  a  globe  valve  are  each  equal  to  a  length 
114 


of  pipe  = 


for  various  pipes — 


This  length  works  out  as  follows 


in. 

in.  j  in. 

in. 

in. 

in. 

in. 

in. 

m. 

in. 

in. 

in. 

in. 

in. 

d  =  I 

i  ij 

2 

at 

3 

A 

5 

6 

8 

IO 

12 

15 

18 

L  =  20 

25  34 

41 

47 

52 

60 

66 

7i 

79 

84 

88 

92 

95 

An  elbow  is  equivalent   to  f  of   a  globe    valve 
These  equivalent  lengths  are  all  added  to  the  straight 
pipe  length,  and  the  total  is  the  equivalent  straight 
pipe. 

Thus  a  4-inch  pipe  40  feet  long  (120  diameters) 
with  a  globe  valve  and  three  elbows,  and  the  open- 
ing from  the  boiler  is  equivalent  to  a  length  of 
120  +  60  +  60  +  (3  x  40)  =  360  diameters,  or  ij 
times  the  tabular  length.  The  flow  through  this 
pipe  will  be  that  given  in  the  table  multiplied  by 
i  +  >/i«5,  or  81-6  per  cent,  of  the  tabular 
number. 

That  is,  for  any  length  of  pipe  other  than  240 
diameters,  divide  240  by  the  equivalent  length,  and 
take  the  square  root  of  the  quotient,  which  divide 
into  the  tabular  weight.  The  result  is  the  weight 
of  flow  for  the  new  length. 

Again,  for  any  loss  of  pressure  other  than  i  pound, 
multiply  the  tabular  figure  by  the  square  root  of 

13 


STEAM    PIPES 

the  pressure  drop.     Thus  a  drop  of  four  pounds 
instead  of  one  pound  should  double  the  output. 
The  formula  (i)  is  sometimes  written  — 

W  =  303-25    d*    \/D  &  ~         where  L  is   the 


number  of  times  the  length  is  of  the  diameter.  Ob- 
viously this  brings  the  term  d  into  the  denominator, 
and  enables  the  d5  to  come  from  under  the  root  sign, 

for  d2  =  \/~. 

it 

The  number  303-25  is  the  87  of  the  previous  for- 
mula multiplied  by  v'lz,  which  is  necessary  where 
it  is  changed  to  feet  instead  of  being  a  multiple  of 
a  diameter  in  inches. 

When  steam  flows  from  one  pressure  to  any  other 
pressure  less  than  three-fifths  of  the  initial  pressure 
its  velocity  has  the  constant  value  888  feet  per 
second,  so  that  the  weight  discharged  varies  with 
the  density.  Hence  the  rule  for  weight  of  outflow 
per  minute  W  pounds. 

W  =  area  of  opening  a  x  370  x  weight  of  a 
cubic  foot  of  steam. 

Rankine's  formula  is  W  =  -  -,  where  a  is  the 

area  in  square  inches  and  p  is  the  absolute  pressure. 
A  coefficient  of  reduction  k  =0-93  is  employed  for 
a  short  pipe  and  k=  0-63  for  an  opening  in  a  thin 
plate,  as  a  safety  valve  for  example.  When  the 
steam  flows  into  a  pressure  more  than  two-thirds 
the  initial  the  formula  becomes— 


THE    FLOW    OF    STEAM     • 


W=  1-9  a  k  ^  (p  —  d)d, 

where  d  is  the  difference  of  pressure.     The  result  is 
substantially  what  all  other  formulae  give. 

In  a  system  of  pipes  in  order  that  a  correct  balance 
may  be  found  the  proper  proportion  of  any  size  of 
pipe  to  allot  as  an  equivalent  of  any  other  size  must 
be  found.  Pipes  deliver  according  to  the  square 
of  their  diameters,  but  the  same  head  will  not  pro- 
duce the  same  velocity  of  flow  in  four  5-inch  pipes 
as  in  their  equivalent  one  lo-inch  pipe. 

The  relative  flow  W  in  different  pipes  varies  as 

where   W  =  weight   of    fluid    and   d  = 


diameter  in  inches. 

In  Table  II.,  from  Steam  (Babcock  &  Wilcox  Co.) 
the  true  or  standard  diameters  of  pipes  are  given, 
and  in  Table  III.  are  given  the  equivalents  of  pipes 
in  terms  of  other  pipes.  That  part  of  the  table 
above  the  diagonal  line  refers  to  standard  pipes  of 
the  nominal  diameter  only.  Below  the  diagonal 
the  pipes  are  actually  of  the  given  diameter. 

Thus  below  the  top  line  7,  along  the  line  2,  we  find 
29,  or  the  number  of  nominal  2-inch  pipes  equal  to 
a  single  7-inch  nominal,  or  again,  6' 21  pipes  of 
standard  7-inch  size  =  i  pipe  of  actual  14-inch  size, 
but  it  requires  6-45  pipes  of  7-inch  standard  to  equal 
one  standard  14-inch. 

The  table  is  useful,  but  it  is  calculated  for  American 
pipes  and  must  be  used  with  discretion  with 
English  pipes,  though  no  very  serious  discrepancy 
will  arise. 

15 


STEAM    PIPES 


TABLE   II.   OF  STANDARD   SIZES,   STEAM  AND  GAS 

PIPES. 


Diameter. 

Diameter. 

Diameter. 

Size, 
Ins. 

Inter- 

Exter- 

Size, 
Ins. 

Inter- 

Exter- 

Size, 
Ins. 

Inter- 

Exter- 

nal. 

nal. 

nal. 

nal. 

nal. 

nal. 

4 

•27 

•40 

2* 

2-47 

2-87 

9 

8-94 

9-62 

i 

•36 

•54 

3 

3-07 

3-5 

10 

IO-02 

1075 

1 

•49 

•67 

3* 

3-55 

4 

ii 

II 

n-75 

J 

•62 

•84 

4 

4-03 

4-5 

12 

12 

12-75 

1 

-82 

1-05    i 

4i 

4-5i 

5 

13 

I3'25 

14 

I 

i'05 

I'3I 

5 

5-04 

5-56 

14 

I4-25 

15 

ij 

1-38 

1-66 

6 

6-06 

6-62 

15 

15-43 

16 

i* 

1-61 

1-90 

7 

7-02 

7-62 

16 

16-4 

17 

2 

2-07 

2-37 

8 

7-98 

8-62 

17 

I7-32 

18 

Mr.  Geipel  gives  the  following  rules  : — 
d   =  diameter  in  inches. 
L  =  length  in  feet. 
p  =  loss  of  pressure  due  to  friction. 
D  =  weight  of  steam  in  pounds  per  cubic  foot. 
Q  =  pounds  of  steam  per  hour. 
v   =  velocity  of  flow  in  feet  per  minute. 


9000-000     d*  D 
v   =  9170  V  j—j^y  whence  the  Tables  IV.,  V.  are 

JLt  LJ 


deduced. 


16 


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17 


STEAM    PIPES 


TABLE  IV. 


Absolute  Pressure.     Pounds  per  Square  Inch. 

Diameter 
of  Pipe. 

2 

5 

7.0 

100 

2OO 

Inches. 

Velocity  in  Ft.  per  Minute  with  i  Ib.    Loss  of  Pressure  per  100  Ft. 

I 

I2OOO 

7790 

4070 

1900 

1380 

2 

I7OOO 

IIOO 

5760 

2690 

1950 

3 

20850 

13520 

7070 

3290 

2390 

6 

2950O 

I9IOO 

990O 

4660 

3380 

9 

36IOO 

23400 

I2O5O 

5700 

4140 

12 

4I60O 

26900 

I4IOO 

6580 

4770 

15 

46600 

3O2OO 

15600 

7400 



18 

5IIOO 

33200 

I7IOO 

— 



24 

58900 

38150 

TABLE  V. 


Diam. 


Absolute  Pressure.     Pounds  per  Square  Inch. 


of 

Pipe. 

Inches. 

2   |   5 

10 

20 

50 

100 

150 

2OO 

Pounds  of  Steam  per  Hour  with  i  Ib.  Drop  of  Pressure  per  100  Ft. 

I 

22'8 

35*2 

487 

67'6 

104 

144 

174 

200 

2 

129 

199 

275 

382 

590 

815 

984 

1130 

3 

356 

549 

760 

1054 

1620 

2245 

2715 

3I2O 

6 

2015 

3100 

4290 

5960 

9170 

12700 

15350 

17640 

9 

5550 

8550 

11820 

16400 

25300 

35000 

42300 

48600 

12 

II380 

17500 

24300 

33700 

51800 

71700 

86600 

99600 

15 

19900 

30610 

42400 

58500 

90500 

125500 

I 

18 

31400 

48400 

67000 

93000 

143000 

— 

— 

— 

24 

64400 

99200 

137000 

190500 





— 

— 

The  accompanying  diagrams  are  drawn  from  these 
formulae. 

18 


THE    FLOW    OF    STEAM 


£•  50,000  ft. 


o>  40,000' 


30,000' 


o  20,000' 


10,000' 


I      °' 

> 

100,000* 


&  80,000* 

IH 
3 
GO 

£ 

ft 

"o    60,000* 


4O,OOO* 


2O,OOO* 


8"  12 

Pipe  diam. 


1  6*  20  dia. 


4O*  80"  1 20"  100"  20O* 

Pressure,  absolute, 


STEAM    PIPES 

For  other  losses  of  pressure,  multiply  the  tabular 
numbers  by  the  square  root  of  the  new  loss.  For 
other  lengths  of  pipe  =  L  feet,  multiply  the  tabular 

numbers  by  -/=. 


The  values  of  •/&  are  best  obtained  by  means  of 
logarithms  :  they  are  given  here  up  to  40  inches  in 
Table  VI. 


TABLE  VI.— 


I 

i 

ii 

401-3 

21 

2020-9 

2 

5-66 

12 

498-8 

22 

227O-I 

3 

15-6 

13 

609-3 

23 

2537-0 

4 

32-0 

14 

733-4 

24 

282I-8 

5 

55-9 

15 

871-4 

30 

4929-5 

6 

88-2 

16 

1024-0 

40 

IOII9-3 

7 

129-6 

17 

1191-6 

8 

181-0 

18 

1374-6 

9 

243-0 

19 

1573-6 

10 

316-2 

20 

1788-9 

The  length  of  pipe  equal  to  a  globe  valve  or  to  an 
opening  into  a  pipe  is  given  as  L^  =  8-66 — ^ 


The  length  equivalent  of  an  elbow  is— 

d 


L.  =  576 


i  + 


d 


20 


THE    FLOW    OF    STEAM      f 

For   different    diameters   the   equivalent   lengths 
thus  figure  out  in  Table  VII. 


TABLE  VII. 


Equivalent  Length  to 

Diameter  in 
Inches. 

Globe  Valve  or 
Pipe  Opening. 

Elbow. 

I 

1-9 

i-3 

2 

6-2 

4-2 

3 

7'9 

5-2 

6 

32-5 

21-6 

9 

55-6 

37*0 

12 

79-9 

53-2 

15 

100-5 

69-6 

18 

129-9 

85-9 

24 

180-6 

123-8 

Properly  speaking,  the  opening  to  a  pipe  should 
be  by  a  short  converging  piece,  the  wider  end  of 
which  has  an  area  about  10  per  cent,  greater  than 
the  pipe  in  order  to  allow  for  the  vena  contracta 
effect.  Boiler  mounting  blocks  do  approximate 
to  this  shape,  but  their  good  effect  is  spoiled  by  the 
usually  clumsy  anti-priming  pipe,  which  is  not  led 
up  to  the  mouthpiece  in  an  easy  curve,  and  is  usually 
plugged  into  the  mouthpiece  in  such  a  way  as  to 
destroy  the  effect  of  this. 

The  resistance  of  openings  and  elbows  by  the 


21 


STEAM    PIPES 

above  rule  is  given  in  the  Table  VII.  on  page  21, 
and  it  will  be  observed  that  the  results,  in  the 
smaller  sizes,  are  much  below  the  figures  given  on 
page  31. 


CHAPTER    III 
Materials 

STEAM  PIPES   are  made   of  one  of    the    four 
following  materials  : — 
Cast  Iron,  Wrought  Iron,  Steel,  Copper. 

CAST  IRON. 

No  material  is  so  convenient  or  has  been  so  largely 
employed  as  cast  iron.  Though  a  material  of  no 
flexibility,  cast  iron  is  strong  and  cheap,  and  with 
care  can  be  cast  sound  and  free  from  blemishes. 
The  flanges  are  readily  faced  in  the  lathe,  for  which 
purpose  stout  bars  carrying  the  centreings  are  com- 
monly employed.  Bolt  holes  are  easily  drilled.. 
Pipes  can  be  cast  to  any  convenient  length,  and  in 
brief,  cast  iron  is  without  a  serious  rival  for  general 
purposes  up  to  pressures  of  100  pounds  per  square 
inch  gauge  pressure.  Above  that  pressure  the 
safety  of  cast  iron  admits  of  doubts  ;  above  120 
pounds  very  serious  doubts  are  to  be  entertained. 
The  stresses  in  steam  piping  are  not  so  much  those 
of  pressure  as  those  which  arise  from  expansion 
due  to  temperature  changes  and  from  water  hammer, 
and,  perhaps  even  more  seriously,  from  forcing 
pipes  to  fill  places  which  they  do  not  fit  properly. 
Some  of  these  stresses  are  increased  by  pressure, 
viz.,  those  due  to  expansive  movements,  and  the 
high  temperatures  of  superheat  also  have  the  same 
effect.  Above  100  pounds,  therefore,  cast  iron 

23 


STEAM    PIPES 

should  not  be  employed.  True,  junction  pieces, 
valve  bodies,  etc.,  are  still  made  by  reputable  firms,  of 
cast  iron  up  to  200  pounds  pressure,  and,  while  the 
author  would  condemn  this  practice,  it  is  perhaps 
but  fair  to  state  that  in  such  cases  the  choice  of 
metal,  the  care  in  casting,  and  the  rej  ection  of  faulty 
bodies,  combine  with  the  abnormal  stoutness  of 
parts  to  render  such  castings  very  much  less  unsafe 
than  ordinary  pipe  castings  from  a  jobbing  foundry, 
with  more  or  less  uncertain  coring  and  no  special 
selection  of  the  iron. 

For  exhaust  pipes,  however,  cast  iron  holds  the 
field.  Exhaust  pipes  are  usually  larger,  much 
larger  than  the  steam  pipe  to  the  same  engine,  for 
it  is  their  duty  to  carry  the  same  steam  in  a  wet 
condition  and  at  much  smaller  pressures.  To  enable 
exhaust  pipes  to  be  tightly  jointed  the  flanges 
require  to  be  stout  and  to  be  faced.  They  should 
be  cast  from  metal  of  good  quality  and  tough,  and 
not  too  hard  to  tool  easily.  Pipes  should  be  cast 
vertically  if  they  are  to  be  reasonably  safe  against 
floating  of  the  cores.  The  common  fault  of  cast- 
iron  pipes  is  the  chaplet,  which  does  not  become 
melted  fast  in  the  pipe  and  causes  blow  holes,  which 
admit  air  and  vitiate  the  vacuum. 

D  P 

A  usual  rule  for  pipe  thickness  is    — - — -  =  0*5, 

4000 

when  D  =  diameter  in  inches,  and  P  =  pressure, 
but  this  rule  will  give  too  small  a  thickness  for  ex- 
haust pipes,  and  no  pressure  should  be  assumed 
less  than,  say,  4  pounds  per  square  inch  for  each  inch 

24 


MATERIALS 


of  diameter  of  pipe.  Flanges  are  made  one-third 
thicker  than  the  pipe  body.  Their  duty  is  greater 
than  the  mere  withstanding  of  pressure  stress.  In 
practice  they  are  subject  to  very  severe  stresses  of 
error  which  arise  when  pipes  do  not  fit  their  places 
and  joints  are  screwed  up  much  too  severely  for 
good  workmanship. 

TABLE    VIII. 
THICKNESS  OF  CAST-IRON  PIPES. 


in.              in. 

in. 

in. 

in. 

in. 

Diameter  . 

4           5 

6 

7 

8 

9 

Thickness  . 

1           A 

i 

i 

& 

* 

Diameter  . 

10             12 

14 

16 

18 

20 

Thickness  . 

f                1 

1 

1 

I 

i 

Neither  of  the  above  rules  is  suited  for  a  large 
range  of  diameters.     A  more  adaptable  rule  is  to 

make  the  thickness  of   the  pipe  "]"= -^~.     This 

rule  serves  for  pipes  from  2  to  12  inches,  up  to  100 
pounds  pressure. 


Above  100  pounds  the  rule   is  T  = 


P.P. 

4000 


+ 


as  given  above,  but  these  last  rules  give  a  pipe  un- 
necessarily heavy  for  exhaust  purposes,  for  which 


the  author's  rule  is  T= 


d  D2  i 

—  —  -  +  0-5  —  —  -g,  the  result 


being  taken  only  to  the  nearest  sixteenth  of  an  inch. 

Thus  a  20-inch  pipe  has  a  thickness   ?— 22_)_  0-5  — 

4000 

—  =  -875".     The  nearest  sixteenth  to  this  is  J  inch, 
and  this  rule  gives  close  results  to  ordinary  practice, 

25 


STEAM    PIPES 

as  per  Table  VIII.,  which  is  that  given  by  the 
Babcock  &  Wilcox  Co.  for  exhaust  pipes. 

Cast-iron  pipes  can  be  obtained  in  the  form  of 
tees,  small  radius  bends  and  large  radius  bends. 
Straight  pipes  are  made  in  g-feet  lengths,  or,  for 
sizes  below  3-inch  bore,  in  lengths  of  6  feet.  Making- 
up  lengths  are,  of  course,  made  to  any f  templet' 
length  (see  Templet).  Crosses,  pockets,  and  Y" 
pieces  are  also  made,  and  the  Table  XXIlA.,  later 
and  figures  1-7,  herewith,  give  the  sizes  of  such 
pieces  as  made  by  the  Babcock  Company.  It  will  be 
noted  that  all  pieces  of  the  same  main  size  must 
always  have  equal  overall  dimensions.  Thus  the 
projection  of  the  branch  on  a  lo-inch  J_  will  always 
be  made  13  inches,  whether  the  diameter  of  the  branch 
piece  be  2  inches,  7  inches,  or  10  inches,  and,  simi- 
larly, the  dimensions  A  Ai  of  a  cross  will  always 
be  the  same  as  the  dimension  A  of  a  T,  while  of 
course  the  dimension  B  will  always  be  half  of  A. 
Unless  these  precautions  are  taken,  piping  systems 
are  liable  to  prove  very  inconvenient  to  put  together. 

Some  engineers  do  not  hesitate  to  employ  cast- 
iron  junction  pieces  for  the  highest  pressures,  taking 
care  to  relieve  the  cast  pieces  of  the  stresses  of 
expansion,  but  the  author  does  not  recommend  this. 
When  so  used  they  are  made  specially  stout,  while 
stout  pieces  are  used  for  lower  pressure  and  lighter 
castings  for  exhaust  steam.  There  is  always  some 
risk  of  a  light  casting  getting  into  a  high  pressure  line. 

Engineers  differ  as  to  the  mode  of  facing  flanges. 
A  flange  faced  right  across  makes  an  excellent  joint 

26 


MATERIALS 


MHn 


~   T 


T 
<if 
1 


fih 


--i^-Hh 

xT\      J 


__i__j 


t^ 

VO 

vrj. 


T' 


-ie> 


27 


STEAM    PIPES 

with  woodite  for  steam  pipes,  or  with  a  plain  ring  for 
exhaust  pipes.  Some  engineers  recess  their  flanges 
in  the  form  of  a  shallow  spigot  and  socket,  as 
shown  in  Fig.  50,  by  Yates  &  Thorn.  This  certainly 
is  a  safeguard  against  blowing  out  the  joint  ring. 
Such  pipes  are  often  difficult  to  take  down  or  to  fit 
with  a  new  ring.  The  Babcock  Co.  have  a  narrow 
facing  strip  only  round  the  pipe,  and  make  the  joint 
with  a  light  corrugated  ring  of  brass  or  copper,  all 
the  bolt  pressure  being  concentrated  on  the  narrow 
face.  See  Figs,  u,  12. 

In  Table  IX.  are  given  the  dimensions  of  the  cast- 
iron  exhaust  tees  of  the  standard  of  the  British 
Electric  Traction  Co.,  kindly  supplied  me  by  Mr.  A. 
J.  Lawson,  of  that  Company,  and  shown  in  Fig.  8. 

The  only  remark  that  might  be  made  on  these 
is  that  bolts  of  J-inch  diameter,  as  needed  for  the 
f  holes,  are  smaller  than  is  perhaps  desirable,  noth- 
ing less  than  fth  bolt  diameter  being  very  satis- 
factory in  practice,  though  the  smaller  size  was 
put  in  to  be  proportional  to  the  rule  of  bolt  numbers 
in  multiples  of  four. 

This  Company  face  pipe  flanges  straight  across, 
with  no  projecting  ring  and  no  recess.  Flanges 

faced  flat  across  are  often  scored  with  two  or  three 

» 

circular  grooves  put  in  to  the  depth  of  -^  or  ^  with 
a  single  V-point  tool,  with  the  object  of  better  hold- 
ing the  joint  rings.  These  grooves  should  only  be 
employed  where  soft  rings  can  be  used.  That  is, 
they  must  not  be  used  where  joints  are  made  with 
simple  copper  wire,  for  steam  will  leak  at  the  joint 
where  a  wire  may  run  across  a  groove. 

28 


MATERIALS 


FIG.    8. CAST-IRON    EXHAUST    TEES    OF    BRITISH    ELECTRIC    TRACTION    CO. 

TABLE    IX. 
CAST-IRON  EXHAUST  TEES. 


Size. 

A 

B 

C 

D 

E 

F 

G 

Bolt  Holes. 

24 

2j 

9 

4* 

7 

5i 

I 

f 

f  1 

3 

3 

9 

5 

74 

6 

A 

i 

1   4 

34 

3* 

10 

5 

8 

6J 

* 

1 

i  J 

4 

4 

ii 

54 

9 

7i 

4 

i 

*  i 

44 

4i 

ii 

6 

94 

8 

i 

1 

f 

5 

5 

13 

64 

104 

8| 

i 

1 

1 

0 

6 

6 

14 

74 

12 

IO 

i 

1 

1 

o 

7 

7 

15 

8 

13 

I0| 

* 

f 

1 

8 

8 

16 

84 

14 

12 

* 

f 

1  J 

9 

9 

18 

9 

15 

13 

* 

I 

1  } 

10 

10 

19 

10 

i6i 

141 

i 

I 

1 

ii 

ii 

20 

10 

17 

15 

I 

I 

t 

12 

12 

22 

ii 

X9i 

*7 

f 

il 

J 

.12 

13 

13 

23 

12 

20j 

18 

i 

ii 

1 

14 

14 

24 

13 

2li 

19 

1 

ij 

1 

16 

16 

27 

14 

24 

2li 

1 

if 

I 

29 


STEAM    PIPES 

In  case  of  reducing  tees,  no  difference  to  be  made 
in  the  dimensions  B  or  C. 

Bolts  £  smaller  than  holes. 

In  Table  X.  and  Fig.  9  the  standards  of  the  same 
Company  are  given  for  cast-iron  steam  tees,  and  in 


# 


f/S£S////s/s////////777)(/// 

M 


T 


FIG<    9. CAST-IRON    STEAM   TEES    OF   BRITISH   ELECTRIC   TRACTION    CO. 

TABLE    X. 

CAST-IRON  STEAM  TEES  TESTED  TO  200  LB. 


Bolt  Holes. 

Size. 

A 

B 

c 

D 

E 

F 

G 

H 

I 

N 

S 

3 

3 

9ft 

5* 

7J 

6J 

4 

i 

ii 

I 

8 

1 

3i 

31 

IO 

)> 

7l 

6| 

>J 

» 

5J 

J) 

?> 

i 

3* 

3i 

IO 

6 

8 

61 

» 

» 

» 

* 

» 

» 

3f 

3l 

II 

» 

8ft 

7 

A 

}» 

J> 

» 

j  j 

j> 

4 

4 

II* 

6J 

9 

7t 

JJ 

I 

Ii 

5) 

?> 

5> 

5 

5 

13 

7i 

IOJ 

8| 

i 

J) 

If 

i 

5> 

J 

6 

6 

15 

8 

12 

IO 

i 

I* 

Ii 

)J 

)5 

I 

7 

7 

16 

8ft 

13 

II 

» 

Ii 

J  J 

J) 

12 

I 

8 

8 

18 

9 

14 

12 

1 

Ii 

If 

1 

j) 

I 

30 


MATERIALS 


Table  XL  and  Fig.  lothe  same  Company's  standard 
for  mild  steel  tees  with  standard  flanges. 

It  will  be  noticed  that  these  standards  appear  to 


FIG.    IO. MILD    STEEL   STEAM   TEES    WITH    STANDARD    FLANGES    OF   BRITISH 

ELECTRIC    TRACTION    CO. 

TABLE  XI. 
MILD  STEEL  STEAM  TEES  WITH  STANDARD  FLANGES. 


Size. 

A 

B 

c 

D 

E 

N 

s 

1 

1 

5i 

3 

4i 

2| 

4 

f 

I 

I 

6 

55 

41 

31 

j) 

55 

ij 

II 

7 

3i 

4l 

3i 

55 

»5 

it 

It 

55 

4 

5i 

4 

5  5 

1 

if 

If 

8 

4i 

6 

41 

5  5 

55 

2 

2 

,, 

4i 

61 

5 

8 

f 

2j 

2j 

81 

55 

j» 

j  j 

,, 

J5 

2j 

21 

9 

5 

7 

51 

55 

55 

2} 

2j 

91 

55 

7i 

51 

55 

55 

have  been  designed  somewhat  on  the  idea  of  each 
size  standing  by  itself  of  the  best  proportion  accord- 
ing to  the  designer's  views  for  the  particular  piece. 


STEAM    PIPES 

Thus  the  dimension  C  is  not  made  one-half  of  B  in 
every  case,  as  it  ought  to  be  in  the  author's  opinion. 
C  is,  however,  always  made  the  same  for  every  tee 
of  a  given  size  A ,  no  matter  what  the  diameter  of 
the  branch  or  A±. 

In  event  of  a  +  being  required  it  would  not 
measure  equally  over  each  rim  of  flanges,  or  if  it  did 
do  so  it  would  not  work  evenly  with  the  tees  of  the 
same  size.  Though  good  in  themselves  and  useful 
as  a  guide  in  flange  proportion  and  generally,  these 
standards  should  be  changed  in  such  respects  in 
order  to  secure  uniformity,  so  that  the  set  of  a  T7 
the  half -breadth  of  a  +,  and  the  set  of  a  quarter- 
bend  may  all  measure  alike. 

Mr.  Venning  advises  that  as  regards  bends  in 
pipes  which  do  not  need  to  be  proportioned  to  suit 
other  junction  pieces,  the  radius  should  not  be  less 
than  five  diameters  of  the  pipe.  An  easy  bend  is 
better  for  the  flow  of  steam.  Small  quarter-bends, 
however,  when  in  particular  situations,  have  to 
accommodate  themselves  to  the  size  of  other  junc- 
tion pieces,  hence  the  dimension  \A  in  Fig.  4  corre- 
sponds with  the  dimensions  of  Figs,  i  and  2,  which 
may  be  looked  on  as  the  leading  junction  pieces. 

COPPER. 

As  a  material  for  steam  pipes,  copper  has  long 
held  a  place  it  can  no  longer  claim  with  high  tem- 
perature steam.  Copper  pipes  are  flexible  because 
weak,  and  have  been  much  used  for  lengths  or 
bends  intended  to  give  way  under  stress. 

32 


MATERIALS 


Copper  for  pipes  must  not  contain  more  than 
0-7  of  i  per  cent,  of  impurity,  and  the  pipes  should 
be  solid  drawn.  A  rule  for  brazed  pipes  is 

D  x  P 

|-o- 1 25".  where  D  =  pipe  diameter  in  inches 

10000 

and  P  =  pressure  by  gauge  per  square  inch. 

Brazing  must  be  looked  on  with  great  suspicion, 
though  it  may  be  employed  in  attaching  flanges, 
which  should  be  four  times  as  thick  as  the  pipes. 

At  a  temperature  of  360°  F.  the  strength  of  copper 
is  reduced  15  per  cent.  Copper  is  therefore  to  be 
employed  cautiously  for  high  pressures,  and  it  is 
not  a  suitable  material  for  conveying  superheated 
steam. 

The  diminution  of  tenacity  is  shown  in  the  an- 
nexed table. 

DIMINUTION  OF  STRENGTH  OF  COPPER  AT  TEMPERA- 
TURES  ABOVE   32°. 


Loss  of 

Loss  of 

Temperature. 

Tenacity. 

Temperature. 

Tenacity. 

Per  cent. 

Per  cent. 

68° 

2 

638° 

35 

138° 

5 

748° 

45 

248° 

IO 

788° 

50 

328° 

15 

838° 

55 

418° 

20 

938° 

66 

438° 

22 

968° 

68 

488° 

25 

1168° 

88 

The  above  figures  must  always  be  allowed  for  in 
calculating  pipe  strengths,  the  bursting  pressure  of 
which  is  found  by  the  following  rule : — 

33  D 


STEAM    PIPES 

4-     V>     /^      \^     Q 

•    ,  —  where  t  =  thickness  in  inches. 
a 

s  =  tenacity  in  pounds  per  square 

inch. 

d  =  pipe  diameter  in  inches. 
Good  ordinary  metal  has  the  following  values 
for  s  : — 

Cast  Iron  =  15,000. 

Copper  (cold)  =  30,000. 

Wrought  Iron  =  49,000. 

Mild  Steel  =  60,000. 

In  modern  practice  with  superheated  steam 
copper  must  not  be  assumed  to  have  a  tenacity 
above  16,500  pounds,  and  brazing  at  superheat 
temperatures  becomes  rotten. 

In  Admiralty  practice  copper  pipes  are  wound 
with  steel  wire  close  laid  as  a  precaution  against 
ripping. 

Mr.  Ferranti,  to  avoid  danger  from  large  copper 
pipes,  built  up  large  pipes  of  a  number  of  small  pipes 
closely  spaced  in  flange  plates,  which  when  bolted 
together  gave  a  large  number  of  pipes  in  cluster, 
but  the  system  was  expensive. 

Solid-drawn  copper  pipes  are  said  to  be  liable 
to  longitudinal  splits. 

The  ductility  of  copper  is  not  great.  When  pulled 
apart  by  tension  its  reduction  of  area  at  fracture  is 
small,  and  copper  has  lost  any  superior  value  it  once 
possessed,  perhaps  very  properly  as  compared  with 
cast  iron,  in  comparison  with  which  copper  first 
gained  its  character  for  elasticity  and  safety, 

34 


MATERIALS 

Mr.  W.  E.  Storey  states  that  a  common  cause  of 
deterioration  of  copper  is  its  contact  when  hot  with 
reducing  gases,  such  as  coal  gas,  which  makes  the 
metal  brittle.  The  same  result  is  produced  in  the 
brazing  hearth,  when  the  air  supply  is  insufficient. 
Such  copper  is  properly  to  be  termed  gassed,  rather 
than  burnt,  and  this  would  tend  to  explain  a  fact 
and  avoid  a  danger.  He  attributes  failures  in 
steam  pipe  to  improper  design,  and  urges  solid-drawn 
tubes  for  bends  with  a  radius  at  least  three  diameters 
of  the  pipe.  He  deprecates  severe  hydraulic  tests. 
Though  he  is  a  maker  of  copper  pipes,  his  advocacy 
is  far  from  urgent,  and  engineers  would  be  well 
advised  to  avoid  copper  for  steam  pipes,  and 
especially  superheated  steam  pipes,  but  copper 
may  still  be  well  employed  for  pipes  containing 
water,  such  as  feed  pipes,  the  spring  piece  of  a 
boiler  blow-off — not  on  the  boiler  side  of  the  blow- 
off  cock,  however. 

Electro-deposited  copper  pipes  .are  said  to  be 
50  per  cent,  stronger  than  ordinary  copper.  The 
author  has  used  such  copper  only  in  water  work, 
and  cannot  speak  to  its  use  in  steam  work. 

FLEXIBLE  METALLIC  PIPES. 

Flexible  pipes  are  made  by  coiling  into  a  closely 
interlocked  helix  a  peculiarly  folded  strip  of  metal. 
This  may  be  steel,  zinc,  brass,  copper  or  a  bronze 
alloy.  These  pipes  are  suitable  even  up  to  300 
pounds  steam  pressure.  They  are  very  flexible, 

35 


STEAM    PIPES 

and  are  maintained  steam  tight  by  means  of  a  pack- 
ing of  asbestos,  which  is  the  more  tightly  held  in 
the  folds  of  the  helix  the  greater  the  pressure  inside 
the  pipe.  Bronze  is  considered  best  for  steam  pipes 
and  these  pipes  are  particularly  suited  for  rapidly 
connecting  boilers  and  engines  on  contractor's 
or  temporary  work.  Flanges  are  attached  by 
means  of  a  screwed  gland  and  collar,  with  asbestos 
packing,  which  holds  firmly  on  the  ridges  of  the 
pipe. 

Any  gap  in  a  length  of  pipe  can  readily  be  made 
good  by  a  piece  of  flexible  pipe  slightly  long.  It 
will  accommodate  itself  to  any  flange  angle.  The 
author  has  no  knowledge  to  go  upon  as  to  long  con- 
tinued durability,  but  there  can  be  no  doubt  that  it 
would  form  a  perfect  connection  between  a  boiler 
and  the  main  steam  pipe. 

If  used  where  it  is  not  supported  at  each  end  it 
might  be  advisable  to  restrain  end  movement,  in 
order  to  keep  the  flange  connections  free  from 
tension. 

Where  a  bad  foundation  causes  settlement  and 
undue  strains,  a  short  length  of  flexible  pipe  would 
prevent  all  trouble  It  is  well  engineers  should  bear 
this  flexible  tubing  in  mind,  for  at  times  it  may  prove 
useful  and  of  marked  convenience. 

WROUGHT  IRON  AND  STEEL  PIPES. 

Pipes  of  steel  up  to  10  inches  diameter  can  be  had 
in  weldless  steel.  Above  that  size,  as  well  as  below 

36 


MATERIALS 


TABLE  X!A. 

WROUGHT  STEEL  PIPES,  WITH  WROUGHT  STEEL  FLANGES. 


Internal  diameter  } 

1 

1 

2 

9* 

3 

3i 

A 

of  Pipe  in  inches  J 

J 

. 

2  ! 

i 

Thickness  of  Pipe  \ 
in   inches    .      .  J 

9W.G. 

8W.G. 

6W.G. 

* 

* 

i 

i 

i 

Weight  per  (  Ib. 
foot    of      I 

1-48 

1-89 

3-31 

5-0 

5-5 

8-5 

IO-O 

II-O 

Pipe        1 

(approx.).    Ikilos. 

•673 

•86 

1-51 

2-3 

2-5 

3-86 

4-55 

5-o 

Weight  per  f  Ib. 

2-8 

5-8 

6-9 

17-0 

20-0 

25-0 

26-0 

38-0 

pair  of      J 

Flanges     | 

(approx.).  [kilos. 

1-27 

2-63 

3-09 

773 

9-IO 

n-35 

n-8 

17-3 

Internal  diameter  "1 
of  Pipe  in  inches  J 

5 

6 

7 

8 

9 

10 

12 

14 

Thickness  of  Pipe  \ 

l 

1  1 

a 

3. 

in  inches     .      .  J 

4 

32 

8 

8 

Weight  per  f  Ib. 

I4-0 

21 

24-5 

27-5 

35-5 

41-0 

49-0 

67-0 

foot     of     1 

Pipe        | 

(approx.).    Ikilos. 

6-35 

7-5 

n-i 

12-5 

16-1 

18-6 

22-3 

30-4 

Weight  per  C  Ib. 

42-0 

53-o 

84-0 

80-0 

96-0 

130-0 

162-0 

154-0 

pair  of      I 

Flanges      j 

(approx.).    Ikilos. 

19-1 

24-1 

38-2 

36-4 

43-6 

59'2 

73-6 

70-0 

i 

37 


STEAM    PIPES 

it,  pipes  can  be  had  lapwelded.  There  is  always 
some  little  doubt  remaining  as  to  the  absolute  sound- 
ness of  a  weld,  and  where  such  doubts  are  felt  the 
riveted  pipe  may  be  relied  on.  The  riveted  pipe, 
when  reasonable  care  has  been  taken  in  choosing 
good  material,  can  be  made  to  show  a  strength 
70  per  cent,  of  a  solid  pipe,  and  it  can  be  relied  on. 
Steel  pipes  and  steel  flanges  are  made  of  all  forms, 
including  straights,  quarter-bends,  quarter-bends 
with  a  length  of  straight,  double  quarter-bends 
joined  by  a  bit  of  straight,  and  set-off  or  cranked 
lengths.  Table  XlA.  (see  previous  page)  will  be 
useful  in  getting  out  approximate  weights  of  pipe. 
It  is  copied  from  a  list  of  the  Babcock  Co. 

Steel  for  pipes  should  be  of  strictly  mild  quality, 
similar  to  boiler  plate,  with  a  tenacity  of  24  to  27 
tons  per  square  inch  and  an  elongation  on  tenacity 
test  of  not  less  than  20  per  cent,  in  a  length  of  eight 
inches. 

The  flanges  of  steel  pipes  are  attached  by 
three  usual  methods,  viz.,  riveting,  welding  and 
screwing. 

In  the  practice  of  the  Babcock  Co.  pipes  below 
6  inches  are  screwed  into  their  flanges  (Fig.  n)  and 
expanded  by  a  tube  expander.  The  Whitworth 
thread  should  be  used.  It  has  n  threads  per  inch, 
in  all  sizes  above  \" .  The  coarser  American  thread 
does  not  produce  such  good  work  or  so  tight  as  the 
English  or  Whitworth  thread.  Pipes  are  faced 
and  drilled  after  fixing  the  flanges. 

Above  6  inches  the  Babcock  Co.  rivet  on  the 

38 


MATERIALS 

flanges  (Fig.  12),  and  they  frequently  also  rivet  on 
branches,  as  in  Fig.  13. 


FIG.    II. — FLANGE    SCREWED    ON.  FIG.     12. FLANGE    RIVETED    ON. 

BABCOCK    &    WILCOX    CO. 


The  flanges  of  steel  pipes  are  stamped  out  of 
solid  forged  pieces,  and  weigh  as  in  the  annexed 
Table  12  for  high  pressure  pipes,  Table  13  for 


FIG.    13. RIVETED    BRANCHES.       BABCOCK   AND   WILCOX  CO, 

lighter  purposes,  and  Table  14  for  heavy  cast-iron 
flanges. 

Riveted    pipes    are    usually    double-riveted  lap- 
jointed  scarfed   down  and  tucked  into  the  flange, 

39 


STEAM    PIPES 

as  in  boiler-making  practice ;  the  longitudinal  seams 
are  thinned  at  the  overlap  and  tucked  into  the  ring 
seams. 

The  Mannesmann  Co.  of  London  make  solid  rolled 
steel  tubes  up  to  12-inch  external  diameter,  from 
0*104  inch  thick  in  2-inch  tubes  up  to  0-312  for  sizes 
above  loj.  These  pipes  can  be  had  with  flanges 


FIG.     14. SOLID    WELDED    FLANGE    (YATES    &    THOM). 

attached  by  any  approved  method.  They  also 
manufacture  pipes,  the  flanges  of  which  are  loose 
and  are  slipped  on  to  the  pipes,  which  are  afterwards 
flanged  or  lipped  up  in  various  ways.  These  flanges, 
or  lips,  are  drawn  together  by  bolts  through  the 
loose  heavy  flanges  and  are  offered  for  use  with  high 
pressures  and  superheated  steam. 

Steel  pipes  are  also  made  with  their  flanges  welded 
solid  with  the  pipe,  as  shown  at  Fig.  14. 

The  steel  pipe  is  par  excellence  the  proper  pipe  for 
high  pressure  and  for  superheated  steam.  The 
tenacity  of  steel  at  60,000  pounds  per  square  inch 

40 


MATERIALS 

gives  steel  pipes  of  ordinary  thickness  a  very  large 
margin  of  strength,  a  6-inch  pipe  at  200  pounds 
pressure,  and  J  inch  thick,  only  carrying  a  unit 
stress  of  2,400  pounds  per  square  inch,  or  a  25-fold 
margin  when  solid  drawn,  and  perhaps  15  to  2O-fold 
if  lap  welded.  The  best  practice  for  junction  pieces 
is  to  make  these  of  wrought  steel,  but  this  becomes 


FTG.      15. HEADER     OF     CRUSE     CONTROLLABLE     SUPERHEATER,     SHOWING 

METHOD    OF    MAKING   JOINTS. 

x" 

expensive  in  the  large  sizes,  and  they  are  often  made 
of  cast  steel,  of  similar  pattern  to  cast  iron,  but 
they  need  not  be  so  stout.  The  medium  dimensions 
of  cast-iron  pieces  should  be  ample  for  cast  steel. 
Some  engineers  consider  it  quite  good  practice  to 
employ  cast-iron  junction  pieces,  which,  if  stout 

41 


STEAM    PIPES 

and  carefully  cast  of  strong  metal,  they  look  on  as 
safe  for  the  highest  pressures.  Perhaps  they  are 
safe  when  due  provision  is  made  to  relieve  expan- 
sion stresses,  but  their  chief  danger  is  perhaps  from 
the  sudden  shock  of  water  hammer.  For  super- 
heated steam  steel  pipes  are  most  desirable,  especi- 
ally in  the  superheater  itself.  As  an  example  of 
the  highest  class  of  pipe  work  the  steel  pipes  of  the 
Cruse  Controllable  Superheater  (Fig.  15)  may  be 
cited.  These  pipes  are  usually  6  inches  external 
diameter,  and  TVinch  thick.  They  are  of  solid  rolled 
weldless  steel.  Their  extremities  are  staved  or 
thickened  up  for  threading,  so  that  the  diameter  at 
the  base  of  the  thread  is  a  little  in  excess  of  the 
external  diameter  of  the  pipe  body.  The  staved 
portion  is  threaded,  and  the  pipes  are  simulta- 
neously screwed  at  both  ends  into  headers  of  i  J-inch 
rolled  steel  plate.  They  are  then  expanded.  The 
cover  box  which  encloses  the  ends  of  two  pipes 
with  the  coupling  box  of  the  internal  2 -inch  water- 
control  pipe  is  of  pressed  mild  steel,  and  the 
joint  between  cover  and  header  plate  is  made  by 
means  of  a  solid  ring  of  -nrinch  round  copper 
wire.  These  joints  have  never  been  known  to 
fail,  and  similar  joints  may  be  made  between 
ordinary  faced  flanges  by  means  of  copper  wire. 
The  writer  has  made  them  with  f  -inch  wire  only 
looped  into  a  circle  and  the  ends  simply  crossed 
over  each  other,  the  bolts  tightening  the  wire 
sufficiently  to  flatten  the  crossing  to  a  steam-tight 
condition. 

42 


MATERIALS 


TABLE  XII. 
HIGH  PRESSURE  STEAM  FLANGES,  PATTERN  A. 


Internal 
Diameter  of 
Pipe. 
Inches. 

Outside 
Diameter  of 
Pipe. 
Inches. 

Diameter 
of 
Flange. 
Inches. 

Approximate  Weight. 

Lb. 

Kilos. 

,O 

2f 

7 

7i 

3-49 

2i 

2f 

71 

9 

4 

3 

3i 

8} 

I2i 

5'5 

3i 

4 

9 

I2i 

574 

4 

41 

10 

i6J 

7'43 

5 

54 

ii 

22 

9'9 

6 

6f 

12 

25 

11-25 

7 

7f 

14 

43 

19-35 

8 

8f 

14 

35i 

16 

9 

9H 

15 

46f 

21 

10 

IOJ 

17 

58 

26 

12 

I2f 

xgi 

72| 

3274 

14 

I4J 

2li 

87i 

39-38 

TABLE    XIII. 
LIGHT  WEIGHT  STEEL  FLANGE,  PATTERN  B. 


Internal 

Outside 

Diameter 

Approximate  Weight. 

diameter  of 

Diameter  of 

of 

Pipe. 
Inches. 

Pipe. 
Inches. 

Flange. 
Inches. 

Lb. 

Kilos. 

I 

i* 

3J 

I 

•45 

I 

I& 

4i 

2j 

I-I3 

1} 

1$ 

4i 

2i 

1-02 

ij 

ij 

5 

2| 

1-24 

2 

2J 

6 

41 

2-14 

2\ 

2f 

7 

6J 

2-81 

3 

3i 

8J 

91 

4-28 

4 

4i 

91 

14! 

6-64 

43 


STEAM    PIPES 


HEAVY  PATTERN  CAST-IRON  FLANGES,  FACED  AND 
DRILLED,  FOR  AUXILIARY,  STEAM,  FEED  AND  BLOW- 
OFF    PIPES. 


TABLE    XIV. 
CAST-IRON  FLANGE. 


Internal 
diameter  of 

Outside 
Diameter  of 

Diameter 
of 

Approximate  Weight. 

Pipe. 

Pipe. 

Flange. 

Inches. 

Inches. 

Inches. 

Lb. 

Kilos. 

t 

I* 

31 

2 

•9 

I 

I* 

4i 

3i 

1-6 

it 

if 

4i 

31 

i-5 

ij 

U 

5 

31 

i-5 

2 

2| 

6 

61 

3'i 

2j 

2j 

7 

8i 

•4 

3 

3i 

81 

14 

6.4 

4 

4i 

91 

18 

8-2 

STEEL  ALLOY. 

Some  boiler  makers  will  provide  what  they  call 
steel  pipes,  which  are  really  malleable  iron,  or  so- 
called  steel  alloy.  They  are  often  tough,  but  are 
difficult  to  face,  and  are  apt  to  suffer  from  bad 
spots,  which  leak  out  steam.  No  doubt  such  pipes 
are  much  superior  to  cast  iron,  but  they  are  not 
equal  to  steel  pipes  with  either  screwed  or  welded 
flanges. 

44 


MATERIALS 

Though  Tables  XII.,  XIII.,  XIV.  are  given  as  the 
Babcock  standards,  it  may  be  doubted  if  it  is 
worth  while  having  flanges  of  different  diameters  for 
auxiliary  pipes,  etc. 

At  Fig.  16  is  shown  the  riveted  flange  as 
made  by  Yates  &  Thorn,  with  the  recessed  face 
and  projecting  shallow  spigot,  which,  while  it  is 


FIG.     1 6. RIVETED    FLANGE    ( YATES    &    THOM). 


apt  to  make  it  difficult  to  pull  pipes  apart,  is  very 
efficacious  in  preventing  joint  rings  from  blow- 
ing out.  Pipes  put  together  with  indiarubber 
rings  in  these  recesses  are  sometimes  very  diffi- 
cult to  part.  Plain  flanges  with  sheet  joints  can 
be  sawn  apart  with  an  old  saw,  which  will  clean 
off  the  flange  faces  ready  for  a  new  sheet  to  be 
inserted. 

45 


STEAM    PIPES 

SOCKETED  JOINTS. 

A  form  of  joint  of  extreme  neatness  not  much 
employed  is  the  socketed  joint.  Sockets  are  usually 
screwed  upon  the  pipe  as  tightly  as  possible,  coming 
to  a  stop  where  the  thread  dies  away  into  the  barrel. 
The  next  length  of  pipe  is  screwed  upon  the  pre- 
viously erected  length,  and  it  is  obvious  that  the 
last  length  must  be  flanged  at  one  end,  for  it  cannot 
be  screwed  two  ways  at  once.  But  the  flange  is 
not  always  even  possible,  and  socketed  pipes  are 
joined  finally  by  means  of  a  "  long  thread "  or 
"  connector/'  which  consists  of  a  piece  of  pipe  of 
any  length,  one  end  of  which  is  threaded  a  long  way 
so  that  the  threaded  portion  will  hold  the  full  length 
of  a  socket  as  well  as  a  back  nut.  In  making  a  final 
joint  by  this  long  thread  the  socket  is  fully  screwed 
back,  the  ends  of  the  pipes  to  be  joined  are  brought 
together,  and  the  socket  is  then  screwed  forward 
upon  the  end  to  be  joined  up.  For  each  thread  it 
advances  on  one  pipe  it  leaves  the  other,  and  of  course 
is  somewhat  slack  upon  the  long  thread.  The  back 
nut  is  then  screwed  against  the  socket,  a  thread 
of  asbestos  with  cement  being  wrapped  round  the 
thread  and  forced  tightly  against  the  socket  end 
by  the  back  nut. 

There  should  be  a  back  nut  at  each  end  of  the 
socket  for  steam  work. 

Artesian  pipes  are  faced  off  to  dead  lengths  of 
10  feet,  or  other  desired  lengths,  and  have  special 
sockets  which  screw  exactly  half  length  on  each 

46  * 


MATERIALS 

pipe  and  tighten  up  on  the  last  of  the  thread  just 
as  the  faced-off  ends  meet  at  the  middle  of  the 
socket.  Such  pipes  could  be  made  to  form  a  steam- 
tight  joint  by  means  of  a  ring  of  copper  between 
the  ends.  It  is  possible  that  socketed  pipes  will 
come  more  into  use  for  special  work,  as  they  are 
very  neat,  offer  the  minimum  of  surface  for  loss  of 
heat,  and  can  be  covered  with  sectional  or  other 
covering  to  look  very  neat,  having  no  flanges.  The 
long  thread  affords  every  facility  for  making  up 
lengths  exactly.  It  is,  however,  certain  that  sock- 
eted pipes  are  troublesome  to  take  apart.  The 
sockets  become  very  fast.  They  are  best  put 
together  with  Dixon's  smear-grease,  a  compound 
of  mineral  oil  and  graphite,  which  is  said  not  to 
become  hard. 

As  regards  wrought-iron  pipes  these  are  lap- 
welded  for  steam  purposes,  are  to  be  treated 
as  described  for  steel,  and  it  is  the  author's 
belief  are  often  supplied  of  steel  to  fill  wrought 
iron  orders. 

FLEXIBLE  METALLIC  TUBING. 

For  temporary  work,  flexible  metallic  tubing 
coiled  up  from  pecular  doubled  or  folded  steel  strip, 
interlocked  and  flexibly  packed  with  a  thread  of 
asbestos  or  other  fibrous  matter,  may  be  employed. 
It  may  be  obtained  attached  to  flanges,  and  for  rapid 
connection  is  easily  put  in  to  occupy  the  place  of 
making-up  lengths  not  yet  arrived  from  the  makers. 

47 


STEAM    PIPES 


1 1  is  best  made  of  bronze  for  steam  purposes,  as  to 
which  a  further  note  is  made  under  the  head  of 
"  Copper/ 

American  pipe  of  ij  and  up  to  2-inch  sizes  is 
screwed  nj  threads  per  inch.  Above  that  size  it  is 
screwed  8  threads,  which  seems  coarse  to  English 
engineers,  and  is  not  so  good  as  our  Whitworth 
ii  threads  for  light  work. 

The  following  is  the  American  pipe  list  abridged 
for  lap-welded  wrought-iron  pipe : — 


Inside 

Outside 

Weight 

Threads 

Diameter. 

Diameter. 

per  Foot. 

per  Inch. 

ii 

I-900 

2-68 

"J 

2 

2-375 

3-6o 

Hi 

2l 

2-875 

5-73 

8 

3 

3-500 

7-54 

— 

3i 

4-000 

9-00 

— 

4 

4-500 

10-66 

— 

4i 

5-000 

12-34 

— 

5 

5-563 

14-50 

— 

6 

6-625 

18-76 

— 

7 

7-625 

23-27 

— 

8 

8-625 

28-18 

— 

9 

9-625 

3370 

— 

10 

10750 

40-06 

— 

ii 

12-000 

45-95 

— 

12 

12-750 

49-00 

— 

13 

14-000 

54-00 

— 

14 

15-000 

58-00 

— 

— 

16-000 

61-77 

— 

— 

18-000 

70-00 

— 

— 

20-000 

77*57 

— 

— 

22-000 

85-47 

— 

~ 

24-000 

93-37 

, 

48 


MATERIALS 

American  pipes  are  screwed  with  a  taper  per  inch 
of  length  of  screw  of  &  up  to  8  inches  diameter 
and  -gr  above  that  size. 

As  with  English  pipes,  the  inside  diameter  of 
American  w.i.  or  steel  pipe  is  not  the  nominal 
diameter,  but  varies  as  the  thickness  of  the  pipes 
varies,  the  outside  diameter  being  constant  for  any 
nominal  size. 


WHITWORTH  PIPE  THREADS. 


Internal 
Diameter. 

External 
Diameter. 

Diameter  at 
bottom  of  thread. 

Threads 
per  Inch. 

4 

•826 

734 

r4 

1 

1-04 

•949 

*4 

I 

I-309 

1-192 

ii 

rj 

1-650 

1-533 

ii 

ii 

1-882 

1765 

n 

2 

2-347 

2-23 

ii 

2j 

3-00 

2-882 

ii 

3 

3'485 

3-368 

ii 

4 

4-340 

4-223 

ii 

Pipes  are  not  made  exactly  to  their  nominal  inside 
diameters.  All  pipes,  whatever  their  strength,  have 
equal  outside  diameters  for  the  same  nominal  in- 
ternal diameter.  Any  change  of  thickness  adds 
to  or  subtracts  from  the  inside  dimensions.  The 
outside  diameter  of  English  and  American  pipes 
differ  very  slightly. 

Messrs.  John  Spencer,  Ltd.,  say  that  for  general 

49  E 


STEAM    PIPES 

work  there  is  nothing  to  beat  lapwelded  steel  pipes, 
with  solid  welded  flanges,  and  branches  riveted  on, 
for  sizes  from  2-in.  bore  to  12-in.  inclusive.  For 
larger  pipes  riveted  flanges  are  preferred,  and  for 
low  pressure  and  small  pipes,  screwed  flanges.  This 
firm's  list  of  standard  flange  diameters,  drilling,  etc., 
and  also  thickness  of  pipes  for  both  high  and  low 
pressure  steam  main  work  is  annexed.  The  thick- 
ness of  pipes  is  given  for  straights ;  bends  are  always 
made  somewhat  thicker  : — 


TO  120  LB.  PRESSURE. 


Bore. 

Diameter. 

Thickness. 

No.  of 
Holes. 

Diameter 
of  Pitch 
Circle. 

Size  of 
Bolts. 

iin. 

3iin. 

i  in. 

4 

2}  in. 

-ft  in. 

1  „ 

3l  „ 

i  ,. 

4 

2|   „ 

TV    „ 

i     » 

4i  » 

4  .. 

4 

9t:N 

i  „ 

Iin 

5    „ 

i  ., 

4 

3f  » 

i  „ 

Ii,, 

5i  >, 

4  „ 

4 

4    » 

i  „ 

2      „ 

6    „ 

1  „ 

4 

41  „ 

i  „ 

2     „ 

6|  „ 

1  „ 

4 

5    » 

i  „ 

2i,, 

6J,, 

1  .. 

4 

5    ,> 

4  „ 

2j   „ 

7    » 

1  „ 

6 

5i  >, 

4  „ 

3      » 

8    „ 

i  ,. 

6 

6J,, 

1  „ 

3l  » 

8i,, 

i,, 

6 

6|  „ 

i  ,, 

4    ,, 

9    » 

i  „ 

6 

7i» 

i  „ 

5    ,, 

ioj  „ 

J  ,. 

6 

8i,, 

i  -. 

6    „ 

12     „ 

i  „ 

8 

10      „ 

1  ,, 

7    „ 

134  » 

i  „ 

8 

nj  » 

i,, 

8    „ 

15     » 

i*,, 

8 

I2f    „ 

J  „ 

9     ,, 

16    tt 

i*,, 

10 

I3l  » 

t  „ 

10      „ 

17    » 

i*,, 

10 

I4J  » 

J  „ 

ii    „ 

18    „ 

ii,, 

12 

I5l  „ 

I  ., 

12      „ 

19    » 

if,, 

12 

i6|  „ 

t  ,, 

50 


MATERIALS 


TO  200  LB.  PRESSURE. 


Bore. 

Thickness 
of  Pipe. 

Thickness 
of  Flange. 

No.  of 
Holes. 

Diameter  of 
Pitch  Circle. 

Size  of 
Bolts. 

i  in. 

10   g. 

J  in. 

4 

2j  in. 

w  in. 

1  „ 

9   *> 

^   5> 

4 

2|    „ 

,, 

i  „ 

8  „ 

,, 

ii 

si  ,, 

2^      »  > 

Ij  >» 

7  «, 

„ 

M 

31  » 

,, 

1  2     »» 

6  „ 

,, 

„ 

4    ,. 

,, 

2      „ 

„ 

1  „ 

II 

41  „ 

I       M 

2      „ 

ii 

1  „ 

II 

5    „ 

„ 

2  j   »> 

5  i> 

,, 

,, 

11 

M 

2g    » 

Jin. 

II 

6 

5i  ., 

II 

3    >, 

,, 

1  „ 

,, 

6J  ,, 

1       ># 

31  „ 

,, 

,, 

„ 

6i  „ 

II 

4    >* 

,, 

,, 

,, 

7i  »> 

,, 

5    » 

ii 

~5    " 

8 

8i,, 

II 

6   „ 

ii 

*    ».» 

ii 

10      „ 

5) 

7    » 

,, 

„ 

„ 

112     »» 

,, 

8    „ 

"fo       >f 

IB    » 

„ 

12}   „ 

I      „ 

9    ». 

II 

M 

10 

X3i  » 

|| 

10     „ 

,, 

,, 

„ 

14!  ,, 

,, 

ii    » 

8     i> 

•*•$    »> 

12 

15}  ,. 

II 

12     „ 

II 

If',, 

12 

16}  „ 

" 

Flange  diameters  as  on  previous  list. 

For  making  steam  joints,  Taylor's  corrugated 
brass  rings  give  the  best  result,  and  they  also  strongly 
advise  the  adoption  of  a  facing  strip  -gi-in.  deep  on 
the  flanges  of  all  high  pressure  pipes. 

The  following  empirical  formula  is  given  for  get- 
ting out  quickly  and  accurately  the  length  of  tube 
in  a  right-angle  bend  ;  it  is  found  to  give  excellent 
results  : — Take  the  sum  of  the  two  arms  and  deduct 
5  inches  for  every  foot  of  radius,  plus  f  inch  for 


STEAM    PIPES 

stretching.     Thus,   for  example  :   a  bend  setting  6 
feet  with  a  radius  of  3  feet— 

6'  o"  +  6'  o"  =  12',  less  i'  3f"  =  10'  8J". 

The  lengths  of  tube  in  the  pipe  will  be  10'  8J". 

In  getting  out  steam  mains,  the  chief  point  to 
watch  is  free  expansion,  which  is  obtained  by  using 
a  sufficient  number  of  lapwelded  steel  bends  of 
large  radii,  or  by  the  insertion  of  special  expansion 
pieces.  The  rate  of  expansion  of  steam  pipes  is 
taken  by  Messrs.  Spencer  as  follows  : — 

Copper.  Steel.  C.  Iron.  W.  Iron. 

•012  in.  -00822  in.  -0077  in.  -0082  in. 

per  10  feet  for  a  rise  of  10  degrees  Fahr. 

The  number  of  joints  is  to  be  minimized  by  using 
as  long  pipes  as  possible.  Appended  is  a  list  giving 
what  may  be  considered  stock  lengths  for  various 
sizes  of  pipes. 

Short  bends  and  cast  steel  elbows  should  not,  of 
course,  be  used  when  they  can  be  avoided,  nor 
should  cast  iron  be  used  for  bends  at  all ;  in  fact 
one  should  always  endeavour  to  eliminate  it  from 
steam  main  work,  especially  where  there  is  high 
pressure  and  superheated  steam,  as  cast  iron  de- 
teriorates very  much  when  carrying  superheated 
steam. 

Two  other  very  important  points  are  the  proper 
supporting  and  draining  of  ranges ;  if  the  former  is 
not  well  done  vibration  will  ensue,  and  if  the  latter 
is  insufficient  water  hammer  is  set  up  ;  excessive 

52 


MATERIALS 

vibration  will  cause  leaky  joints,  and  may  lead  to 
very  serious  consequences. 

The  following  formulae  for  thickness  of  pipes  are 
given  : — 

t   =  thickness  of  pipe  in  inches. 

p  =  pressure  per  square  inch. 

d  =  diameter  (internal)  in  inches. 

For  lap  welded  wrought   iron,  t  =  g— — 

d_ 
3500 

j)  d 
Copper  (brazed)  t  = 


cast-iron,  t  =  f—  + 


i>  d 
„     (solid  drawn)      t  =   g— 

These  are  as  used  by  the  Board  of  Trade,  and  hold 
good,  generally  speaking,  for  bores  up  to  12  -in.,  and 
water  Pipes  of  200  Ib.  per  sq.  in.  Another  very 
fair  formulae  for  cast-iron  up  to  200  Ib.  per  sq.  in. 

water-power,  is  t  =  ^   -  +  \  ]  this  gives  somewhat 

heavier  castings. 

A  good  formulae  for  thickness  of  flanges  on  cast- 
iron  pipes  is  :— 

T  =  1-4  x  t  x  -15, 

where  T  =  thickness  of  flange, 


«         » 
For  bolts  :— 

d  =  -83^  +  -3  d  =  diam.  of  bolt, 
n  =  *6D  +  2  n  =  number  „ 

t  =  thickness  of  pipe. 

D  =  diameter  „ 
53 


STEAM    PIPES 

The  following  bursting  pressure  of  steel  pipes  is 
given  :— 


Diameter,  Pipes 

T     1_ 

6  in. 

7  in. 

8  in. 

9  in. 

10  in. 

ii  in. 

12  in. 

in  Inches. 

Thickness. 

i  in- 

1600 

1372 

1:00 

1066 

960 

8;3 

800 

*  „ 

2400 

2058 

1800 

J599 

1440 

1309 

I20O 

1  „ 

3200 

2744 

2400 

2132 

I92O 

17  5 

1600 

"&  »> 

4000 

3430 

3000 

2665 

2400 

2181 

200O 

!  " 

4800 

4116 

3600 

3198 

2880 

2617 

240O 

iS  >» 

5600 

4802 

4200 

373i 

3360 

3053 

2800 

i  ,, 

6400 

5488 

4800 

4264  3040 

3489 

3200 

13  in. 

14  in. 

15  in. 

16  in. 

17  in. 

18  in. 

19  in. 

Jin. 

738 

685 

640 

6OO 

56i 

533 

505 

•f<f  » 

1107  !  1029 

980 

900 

847 

800 

757 

i   H 

1476  1  1372 

1280 

I2OO 

1129 

1066 

1009 

*  „    l845 

17*5 

I60O 

1500 

I4II 

1333 

1261 

1  „    2214 

2058 

IQ2O 

l8oO 

1693 

1600  1513 

is  »> 

2583 

2401 

2240 

2100 

J975 

1866 

i?65 

i  „ 

2952 

2744 

2560 

240O 

2257 

2133 

2017 

Stock  Lengths,  16  to  17  ft.  up  to  10"  diam. 

15  to  16    „  „    „  n"  to  i2/r  diam. 


54 


CHAPTER   IV 
Expansion 

'TVHE  necessity  of  cooling-off  boilers  for  cleaning 
•*•  and  repair,  and  the  fact  that  some  boilers 
are  spare  and  cold,  causes  the  connecting  pipes  of 
the  boilers  to  the  main  to  vary  in  length,  not  only 
as  between  their  hot  and  cold  conditions,  but  as 
between  one  boiler  and  others.  In  a  length  of  100 
feet  a  steam  pipe  may  expand  2  inches  or  more. 
The  coefficient  of  expansion  of  cast  iron  is  0-00000618 
per  degree  Fahrenheit  =0-0000111  per  i°  C. 
Wrought  iron  expands  0-00000656  per  i°F.  = 
0-0000118  per  i°  C. 

Between  the  temperature  at  which  the  pipes 
were  fixed,  say,  59°  F.  =  15°  C.,  and  the  temperature 
of  steam  at  190  pounds  gauge  pressure  per  square 
inch,  say,  383°  F.=  195°  C.,  the  expansion  will  be 
about  4^  inches  per  100  feet. 

Mr.  Yenning  says  a  good  practical  rule  is  to  allow 
i  inch  for  each  50  feet.  Beyond  the  superheater 
the  expansion  effects  will  be  even  greater,  for  the 
temperature  may  be  653°  F.  =  345°  C.,  a  rise  of 
nearly  600°  F.  =  330°  C.,  or  nearly  6|  inches  per 
100  feet  above  the  cold  length,  for  at  high  tempera- 
tures the  expansion  coefficients  become  greater 
(see  table,  p.  68). 

55 


STEAM    PIPES 


Obviously,  therefore,  such  variations  must  be 
provided  for.  In  the  case  of  a  long  battery  of  boilers 
with  a  straight  main  steam  pipe  athwart  them, 
if  the  middle  of  the  pipe  was  anchored  fast  the  two 
ends  would  extend  considerably.  This  would  push 
outwards  the  branch  pipes  of  the  boilers  to  an  amcunt 
gradually  increasing  as  the  distance  from  the  central 
point  was  increased. 


FIG.  I/. 


FIG.  18. 


FIG.  19. 


FIG.  20. 
FORMS  OF  EXPANSION  BENDS. 


FIG.  21, 


The  branch  pipes  would  give  way  by  their  elas- 
ticity, but  they  would  of  course  exert  a  twisting 
stress  upon  the  mounting  block,  the  vertical  pipe 
above  this,  and  the  valve,  if  this  was  at  the  top  of  the 
vertical  branch.  In  long  lengths  of  main,  there- 
fore, bends  of  the  form  of  Figs.  17  to  21  are  employed. 

56 


EXPANSION 

If  circumstances  are  such  that  one  of  these  expan- 
sion lengths  is  to  be  fixed,  its  place  should  be  as  nearly 
central  as  possible  in  the  main,  which  would  be  an- 
chored, if  anchored  at  all,  at  one-fourth  its  length 
from  each  end,  thus  dividing  it  up  into  four  dis- 
tinct lengths,  and  limiting  expansion  in  any  one 
section  to  one-fourth  the  total.  The  anchoring  of 
a  pipe  in  this  way  prevents  the  steam  pressure  on 
the  extreme  ends  of  the  pipe  from  acting  to  pull 
open  the  expansion  bend,  but  if  anchored  in  such 
a  way  as  to  prevent  lateral  movement  there  would 
be  introduced  a  stress  in  the  nearest  boiler  branch 
pipes.  Anchoring,  therefore,  should  be  longitu- 
dinal only.  In  arranging  for  expansion  bands  the 
loop  should,  if  possible,  be  horizontal,  so  as  to  ob- 
viate water  pockets.  If  vertical,  there  must  be  a 
small  connecting  pipe  looped  down  from  the  straight 
main  to  carry  water  across  the  gap  of  horizontal 
continuity.  The  expansion  bend  cannot  be  allowed 
to  hang  downwards  from  the  pipe  unless  the  bottom 
of  the  loop  is  drained  by  a  trap,  and  this  position 
must  not  be  used,  if  possible  to  be  avoided. 

Figs.  17,  18,  19  are  usual  types  of  bends.  Fig.  20 
is  convenient  where  there  is  a  change  of  level  greater 
than  the  pipe  diameter,  for  the  lateral  displacement 
of  the  loop  may  be  little  or  considerable. 

In  Fig.  15  the  stress,  says  Mr.  Stromeyer,  is  tor- 
sional.1 

1  The  Manchester  Steam  Users'  Association.  Memorandum  by 
Chief  Engineer,  June,  1901. 

57 


STEAM    PIPES 

A  bend  is  more  elastic  than  a  straight  of  eqnal 
length  from  crown  to  crown.  Thus,  if  in  Fig.  17  the 
two  straight  arms  were  connected  by  a  rigid  casting  in 
place  of  by  a  bend,  this  form  would  be  the  most 
rigid  of  all  the  arrangements  shown.  Mr.  Stromeyer 
represents  the  elasticity  of  the  two  straight  arms 
by  2.  Then  each  of  the  forms,  Figs.  18,  19,  20, 
will  spring  an  amount  2  x  6  =  12.  Fig.  17,  con- 
sisting of  two-thirds  straight  pipe  and  one-third 
bend,  will  be  represented  by  2f .  In  Fig.  21  the 
elasticity  is  21. 

The  permissible  stretch  of  any  form  varies  with  the 
mean  height  of  the  loop,  is  inversely  as  the  square 
of  the  diameter  and  independent  of  the  thickness  (in 
all  practical  thicknesses). 

The  force  to  stretch  a  bend  is  proportional,  how- 
ever, to  the  thickness  and  to  the  diameter  squared. 
Bends  are  therefore  made  thin  and  weak  if  they 
have  to  relieve  stress  on  a  weak  point,  such  as  a 
cast-iron  valve  or  junction  piece,  but  for  expansion 
of  long  pipes  the  bends  may  be  of  the  same  material 
and  thickness  as  the  pipes. 

Copper,  once  so  much  used  for  bends,  is  not  so 
very  suitable,  though  it  may  be  made  thin.  Its 
elastic  limit  is  low,  and  it  has  less  spring  than  mild 
steel  or  wrought  iron.  It  is  a  metal  that  grows 
brittle  with  age,  and  it  is  dangerous  at  high  tempera- 
tures. 

With  bends  of  4  feet  crown  to  crown,  and  a  dia- 
meter of  pipe  of  6  inches,  Mr.  Stromeyer  gives  the 
following  (Table  XV.)  of  safe  extensions  of  bends  : — 

58 


EXPANSION 


TABLE    XV. 


Material. 

Two 

Straight 
Pipes. 

Fig.  17. 

Figs.  18,  19. 

Fig.  20. 

Fig.  21. 

Steel     . 

Copper  . 

0-21 
O-I2 

0-42 
0-23 

074 
0-4I 

0-74 
0-41 

2-60 
i*45 

The  values  in  the  table,  except  for  Fig.  21,  may 
be  doubled  where  the  pipes  they  relieve  have  free- 
dom for  lateral  movement,  and,  again,  this  double 
value  may  be  again  doubled  if  the  bends  are  ini- 
tially stretched  by  the  same  amount  they  will  be 
compressed  when  hot,  so  that  a  copper  bend  of 
Figs.  18,  19,  20  type  would,  if  erected  cold  and 
stretched  0-82,  allow  of  a  total  difference  of  length 
between  cold  and  hot  of  1*64  inches,  or  enough  for 
a  length  of  50  feet  of  main. 

In  a  battery  of  four  boilers,  as  very  commonly 
arranged  in  cotton  mill  work,  see  Fig.  22,  as  ar- 
ranged by  Yates  &  Thorn.  The  branch  pipes  of 
the  boilers  are  about  12  feet  long  from  crown  of 
steam  mounting  block  to  crown  of  main  steampipes. 
The  only  relief  necessary  here  is  given  by  the  two 
bends  and  long  straight  piece  of  pipe  between  the 
boiler  main  and  the  engine,  the  starting  valve  of 
which  is  not  in  line  with  the  boiler  main.  A  similar 
double  bend  connects  the  high-pressure  cylinder 
with  the  first  initial-pressure  cylinder. 

Expansion  joints  are  sometimes  made  of  the  form 

59 


FIG.    22  —GENERAL  ARRANGEMENT  OF  COTTON  MILL  PLANT  (YATES  &  THOM). 

60 


EXPANSION 

of  Fig.  23.  These  are  small  and  compact,  but  are 
apt  to  become  choked  with  deposit  and  to  split. 
Larger  expansion  discs  are  made  by  riveting  to- 
gether two  flatly  dished  plates.  These  are  also 
liable  to  choke  with  deposit,  and  they  also  offer 
a  large  surface  to  the  steam  pressure,  which  exerts 


FIGS.  23,  24. — EXPANSION   JOINTS    (YATES    &    THOM). 


a  very  heavy  thrust  and  helps  to  nullify  the  move- 
ment of  pipes  when  these  are  wanted  to  contract. 
They  resist  the  very  movement  they  are  designed 
to  accommodate,  and  they  are  therefore  only  to  be 
recommended  for  exhaust  pipes,  in  which  case  the 
outside  pressure  exceeding  the  inside  pressure  tends 
to  move  the  pipes  in  the  same  direction  as  the  ex- 
pansion will  move  them 

61 


FIG.  25 — END  VIEW 


FIG.    25. TELESCOPIC    EXPANSION    JOINT    (YATES    &    THOM). 

62 


EXPANSION 

Expansion  joints  of  the  form  of  Fig.  25  are  some- 
times used.  This  particular  one,  as  made  by 
Messrs.  Yates  &  Thorn,  consists  of  a  sliding  pipe 
and  stuffing  box  to  provide  movement  on  each  side 
of  the  joint  the  pipe  has  legs  upon  it  which  are  joined 
across  the  joint  by  two  long  bolts  that  must  be 
strong  enough  to  resist  the  steam  pressure  on  the 
area  of  the  pipe.  In  a  length  of  pipe  served  by 
such  a  joint  as  this  the  bolts  would  be  of  a  length 


FIG.  26. — BARTER'S  SWIVELLING  EXPANSION  COUPLING. 

equal  to  half  the  length  of  the  pipe.  This  class  of 
expansion  joint  is  only  advised  where  spring  bends 
cannot  conveniently  be  introduced.  Shorter  ex- 
pansion joints  are  made  complete  in  overall  lengths 
of  from  27  to  32  inches,  according  to  size,  i.e.  about 
20  +  1-5  d  inches,  and  weighing  from  75  to  80 
pounds  per  inch  of  pipe  diameter,  according  to  size, 
•the  larger  ones  being  of  the  heavier  proportion. 
Barter's  joint  is  shown  in  Fig.  26.  This  explains 

63 


STEAM    PIPES 

itself.  The  joint  provides  a  universal  movement 
of  a  pipe  in  the  way  of  bending,  but  this  joint  is  not 
an  expansion  joint  to  be  placed  in  the  length  of  a 
pipe.  It  is  rather  to  be  placed  in  the  branch  pipes 
of  each  boiler,  so  as  to  allow  free  movement  of  the 
main  pipe  without  straining  of  the  branch  pipes. 
Where  economy  is  specially  desirable  these  joints 
would  not  be  necessary  on  the  first  (or  perhaps  also 
the  second)  boiler,  on  each  side  of  the  middle  point 
of  the  main. 

If  this  joint  is  so  arranged  that  when  cold  it  lies 
in  a  straight  line,  or  nearly  so,  with  the  boiler  branch 
pipe,  it  is  obvious  that  when  the  main  steam  pipe 
lengthens,  these  swivelling  joints  will  be  displaced 
laterally,  and  will  be  no  longer  straight  and  in  line. 
The  flanges  they  connect  will  therefore  need  to 
approximate  each  other  by  the  amount  of  the  versed 
sine  of  the  arc  of  swivelling.  As,  however,  the 
boiler  branch  pipe  becomes  longer  also  by  heat 
expansion,  this  angular  movement  of  the  swivel 
piece  will  provide  to  some  extent  for  this  expan- 
sion. Thus,  in  a  swivelling  length  of  30  inches  a 
movement  of  i  inch  in  the  main  steam  pipe  would 
imply  an  angle  of  2  degrees,  the  versed  sine  of  which 
is  -0006  or  0*018  inch.  This  is  only  about  one- 
eighth  of  what  a  branch  pipe  of  5  feet  in  length 
would  expand  at  usual  pressures.  But  if  the  swivel 
piece  be  already  placed  at  an  angle  of  4  degrees, 
when  cold,  its  movement  only  2  degrees  further 
would  increase  the  versed  sine  movement  by  -0048, 
or  eight-fold.  Obviously,  therefore,  a  boiler  branch 

64 


EXPANSION 

of  a  length  of  5  feet,  with  a  3O-inch  swivel-piece 
placed  when  cold  2  inches  out  of  line,  would  allow 
for  a  movement  of  the  steam  main  of  i  inch  when 
hot,  and  would  take  up  the  expansion  of  the  boiler 
branch.  If  boilers  and  engines  are  carefully  fixed 
to  drawn  positions,  as  they  may  be,  and  pipes  are 
made  to  the  same  measures  so  as  to  come  right 
without  final  make-up  lengths,  as  is  also  not  merely 
possible  but  practicable,  then  it  would  be  possible 
so  to  arrange  the  whole  scheme  of  pipes  as,  by  plac- 
ing the  swivel  at  greater  initial  angles  towards  the 
end  of  a  range  of  boilers,  to  eliminate  ail  stresses  of 
expansion.  Even  if  such  stresses  were  reduced  to 
half  or  a  third,  it  would  be  a  desirable  thing  to 
accomplish. 

In  many  power  stations  the  boiler  branch  pipes 
enter  the  main  steam  pipe,  and  the  engine  branch 
pipes  are  taken  out  from  points  very  near  to  them. 
Where  possible,  expansion  is  provided  by  bending 
the  boiler  branches  so  as  to  enter  the  steam  main 
at  the  top.  If  the  engine  pipes  leave  the  main  from 
its  upper  side  also,  the  main  acts  as  a  water  separator, 
and  must  be  drained.  If  the  engine  branches  leave 
from  the  bottom  of  the  pipe,  all  water  must  then 
be  dealt  with  at  the  engine  separators.  Both  the 
boiler  and  engine  branches  may  enter  at  the  opposite 
sides  of  the  main  without  bends.  In  this  case  the 
engine  branches  are  usually  bent  down  to  the  engine 
some  feet  further  on,  and  the  separator  is  placed  in 
the  horizontal  part  of  the  engine  branch.  With 
water-tube  boilers,  where  there  is  a  clear  gangway 

65  F 


STEAM    PIPES 

behind  the  boiler  seating,  the  boiler  branches  have 
been  brought  down  by  bends  to  the  steam  main 
placed  in  the  gangway,  and  the  engine  branches 
have  been  carried  up  from  the  main,  bent  through 
the  engine-room  wall,  thence  carried  a  few  feet,  and 
bent  down  to  the  engine  stop-valve. 

This  arrangement  is  very  elastic,  because  the 
various  vertical  pipes  are  several  feet  long.  The 
main  must  be  carried  above  the  passage  ways  be- 
tween pairs  of  boilers,  at  least  6  feet  above  floor. 
It  must  also  be  drained. 

In  case  of  very  long  mains  the  expansion,  if  not 
otherwise  provided  for,  may  be  allowed  for  by  an 
expansion  T-piece.  The  one  pipe  has  a  closed  end 
and  passes  right  through  the  head  of  the  T,  being 
made  steam-tight  by  glands  at  each  end.  That  part 
of  the  pipe  inside  the  T  is  perforated  by  slots  to 
permit  steam  to  pass  to  the  T  and  to  the  pipe,  which 
is  rigidly  bolted  to  the  single  end  of  the  T.  The 
expansion  of  the  long  pipe  can  take  the  place  of 
sliding,  and  there  is  no  end- thrust. 

The  disadvantage  is,  that  the  steam  has  to  take 
a  sharp  square  bend  and  pressure  is  lost.  Sub- 
stantially the  provision  of  suitable  bends  and  suffi- 
ciently long  branches  is  alone  necessary  for  general 
work,  and  a  scheme  of  pipe  work  must  be  carefully 
thought  out  so  that  expansion  shall  not  be  con- 
centrated at  one  point,  but  shall  be  well  distributed 
throughout  the  system,  bearing  in  mind  always 
that  any  one  boiler  may  be  at  rest  between  two 
working  boilers,  or  vice  versa  ;  and  due  consideration 

66 


EXPANSION 

must  be  given  to  each  movement  that  will  occur 
under  the  extremes  of  conditions. 

The  expansion  of  any  other  bends  than  those  of 
4  feet  x  6  inches  given  in  the  table,  page  59,  can 

be  calculated  by  the   rule   given,  or   E  =  e      x  — 

4       **j 

or  E  =  -  — -i *2— '-,  where  d  is   the  diameter  of  pipe  in 

inches,  Hl  the  loop  height  in  feet,  and  e  is  the 
tabular  expansion  for  6-inch  pipe,  E  being  the  per- 
missible expansion  of  the  pipe  sought.  Then  £,as 
found,  may  be  doubled  or  quadrupled,  according 
as  the  pipe  is  free  for  lateral  movement,  or  is 
extended  when  cold. 

The  calculation  of  the  expansion  of  any  length 
of  pipe  is  made  by  the  following  formulae  :— S  = 
L  t  /,  where  S  is  the  movement  sought,  L  is  the 
length  in  feet,  t  the  range  of  temperature  over  which 
the  expansion  occurs,  and  /  is  the  coefficient  of 
expansion  per  foot  of  pipe  per  degree  of  temperature. 
In  a  long  main  taking  branches  from  several  boilers, 
the  middle  of  the  main  may,  as  stated,  be  anchored 
fast.  This  is  easily  effected  when  the  pipe  is  carried 
on  a  bracket,  as  a  cap  may  be  bolted  over  the  pipe, 
but  not  so  as  to  prevent  lateral  movement.  At 
other  points  the  pipe  may  be  suspended  by  rods 
from  brackets  above,  and  a  short  spring  may  be 
placed  between  the  bracket  and  the  nut  of  the 
suspender. 

Anchoring  of  one  point  is  desirable  for  the  pur- 
pose of  checking  the  vibration  which  is  often  set 

67 


STEAM    PIPES 

up  by  the  connection  of  the  pipes  to  the  engines, 
or  by  the  intermittent  impulses  of  the  moving  steam. 
A  pipe  which  swings  in  this  way  may  usually  be 
steadied  without  locking  it  fast,  if  a  stop  is  placed 
against  a  point  of  chief  movement  to  limit  the  ampli- 
tude of  the  vibration  and  destroy  the  natural  rhythm 
of  the  movement. 


EXPANSION  COEFFICIENTS. 

The  expansion  of  cast  iron  between  32°  and  42°, 
or  a  range  of  180°  F.,  is  given  in  Molesworth  as 
o-ooii,  wrought  iron,  0-0012,  and  copper,  0-0018. 

Kempe  gives  the  coefficient  of  linear  expansion 
per  degree  Fahr.  as  follows  :— 


Metal. 

Coefficient. 

Tested  Between. 

Cast  Iron    . 

0-OOOOo6l8 

32°-2I2° 

Steel       .      .      . 

0-OOO006OO 

32°-2I2° 

Wrought  Iron  . 

O-OOOO0895 

32°-572° 

»           »     • 

0-OOO00656 

32°-2I2° 

Copper         ,     .   j     0-00000955 

32°-2I2° 

»j             • 

0-OOOOIO92 

32°-572° 

Firebrick 

0-00000275 

32°-2I2° 

Good  Red  Brick 

0-00000305 

32°-2I2° 

From  this  it  wculd  appear  that  at  temperatures 
of  superheated  steam  the  coefficient  of  expansion 
per  degree  Fahrenheit  for  steam  pipes  may  be  taken 
as  o» 000008,  which  is  nearly  2  inches  in  50  feet  for 
a  temperature  rise  of  400°  F. 

While  undoubtedly  stresses  are  often  very  severe 
and  manifest  themselves  by  failures  of  cast-iron 

63 


EXPANSION 

junction  pieces,  and  by  weeping  joints  and  even 
rivets,  it  must  not  be  necessarily  inferred  that  all 
the  movement  calculated  does  actually  occur  to 
produce  stress.  Much  may  be  done  in  the  way  of 
giving  counter-stresses  initially,  and  cold  to  reduce 
the  working  stresses  when  hot.  Nor  can  we  assume 
that  the  boiler  does  not  move  from  its  cold  position. 
The  expansion  of  firebrick  is  about  half  that  of 
iron,  and  under  boiler  conditions  it  is  much  hotter 
and  its  actual  expansion  is  as  much  or  more.  The 
seating  of  a  Lancashire  boiler  lengthens  as  much 
as  the  boiler,  the  movement  one  way  of  the  steam 
outlet  blcck  on  a  boiler  may  be  as  much  as  the  ex- 
pansion the  other  way  of  the  steam  pipe.  An  ultra 
precision  and  refinement  is  therefore  not  called  for, 
but  it  is  easy  to  see  that  the  expansion  of  the  boiler 
branch  pipe  may  be  very  fairly  balanced  by  com- 
pelling the  boiler  steam-drum  to  expand  from  a 
determined  and  anchored  point.  Practice  has 
taught  what  may  and  what  may  not  be  done,  but 
special  cases  may  require  special  consideration,  and 
for  these  the  methods  indicated  may  be  followed. 
The  use  of  superheated  steam  not  only  increases 
the  pipe  temperatures  but  also  increases  the  co- 
efficient of  expansion,  which  (as  per  table  p.  68) 
becomes  0-000009  nearly  between  cold  and  572°  F. 
Such  an  expansion  as  this  figure  implies  is  very 
considerable.  At  the  same  time,  probably,  the 
pipes  and  bends  are  more  yielding  and  take  up  the 
stresses  by  further  movement.  Where  super- 
heaters are  placed  behind  the  boilers,  as  in  case  of 

69 


STEAM    PIPES 

Lancashire  type  boilers,   the  pipes   to   the   super- 
heater   have    only    the    ordinary    expansion.     But 


n        .ct        M 


Temperature  £Q 
70 


EXPANSION  f 

the  superheater  is  connected  with  the  main,  and 
this  is  to  be  considered  in  the  design. 

The  annexed  diagram  will  be  of  use  in  ascertaining 
the  temperature  of  saturated  steam  from  the  known 
pressure.  With  the  prospect  of  superheat  being 
added,  the  temperatures  found  by  the  diagram 
should  be  increased  by  about  150°  F.  when  calcula- 
ting probable  expansions  to  be  provided  for. 


CHAPTER    V 
Strength   of  Pipes 

THE  thickness  of  a  steel  or  wrought-iron  pipe 
necessary  for  screwing  is  more  than  sufficient 
for  all  ordinary  sizes  at  high  pressures. 

The  stress  on  the  material  of  a  pipe  per  inch  of 
length  is  the  product  of  the  diameter  and  the  pres- 
sure per  square  inch.  This  product,  divided  by 
twice  the  thickness  of  the  pipe,  gives  the  unit  stress. 

Good  wrought  iron  may  be  assumed  to  have  an 
ultimate  strength  of  20  tons  per  square  inch,  and 
steel  of  28  tons.  On  this  basis,  with  a  marginal 
factor  of  5,  the  stress  permissible  will  be  about  9,000 
pounds  for  iron  and  15,000  pounds  for  steel.  Double 
riveted  joints  have  a  70  per  cent,  efficiency,  and  if 
lapwelding  be  allowed  to  have  the  same,  the  unit 
working  tenacity  will  be  6,300  pounds  and  10,500 
pounds  respectively. 

Thus  a  12-inch  pipe  at  200  pounds,  if  only  J-inch 
thick,  only  carries  a  unit  stress  of  4,800  pounds. 
For  very  large  work,  even  to  24-inch  pipes,  the  stress 
on  pipes  J-inch  thick  would  only  be  9,600  pounds  at 
200  pounds  pressure,  or  within  the  working  stress 
of  mild  steel.  Steam  pipes  of  ordinary  manufac- 

72 


STRENGTH    OF    PIPES 

turer's  thickness  of  tube  walls  are  thus  of  ample 
and  excessive  strength  when  only  double  riveted. 
Bad  welds  should  be  provided  against  by  hydraulic 
test  up  to  12,000  pounds  in  iron  and  21,000  pounds 
in  steel,  as  calculated  on  the  actual  thickness,  which 
will  usually  exceed  J-inch  in  pipes  of  even  10  inches 
diameter. 

Very  large  pipes  may  be  worth  riveting  with  butt 
strips.  Solid  rolled  pipes  can  be  calculated  to  stand 
a  unit  stress  of  15,000  pounds,  and  need  not  exceed 
the  thickness  proper  to  this  stress  so  long  as  the 
threading  at  the  flanges  does  not  unduly  reduce 
them  and  render  them  liable  to  crack  off  at  the 
flange.  Probably  steam  pipes  are  made  too  heavy, 
and  being  so  they  throw  undue  stresses  on  cast-iron 
junction  pieces,  which  are  therefore  made  unduly 
clumsy  to  stand  the  stresses. 

Solid  rolled  pipes  with  flanges  double-riveted 
appear  to  offer  the  maximum  strength  per  unit  of 
weight.  Flanges  screwed  on  to  large  thin  pipes 
involve  the  weakening  due  to  the  threading. 

The  Whit  worth  thread  is  the  best  for  pipe  threads, 
as  it  is  finer  than  the  American  thread  and  cuts  less 
of  the  pipe  away.  Its  main  dimensions  are  given 
here  within  Table  XVI.,  up  to  4  inches.  All  larger  sizes 
have  the  same  thread  of  n  threads  per  inch.  Pipes 
of  all  kinds  are  of  the  same  diameter  outside.  The 
nominal  inside  diameter  becomes  less  as  the  pipe  is 
made  stronger.  Threads  may  thus  be  all  standard, 
but  some  pipe  makers  do  not  make  to  the  Whit- 
worth  standard  even  to-day. 

73 


STEAM    PIPES 


TABLE  XVI. 
WHITWORTH  PIPE  THREADS. 


Size. 

No.  of 
Threads 
per  Inch. 

External  Diain. 

Diameter 
at  Bottom  of 
Thread. 

4 

14 

0-8257 

0-7342 

1 

14 

I-04I 

0-9495 

I 

II 

I-309 

1-1925 

ii 

II 

I-650 

1-5335 

ii 

II 

I-8825 

1-765 

2 

II 

2-347 

2-2305 

A 

II 

3-0013              2-8848 

3 

II 

3-485 

3-3685 

34 

II 

3-912 

3-7955 

4 

II 

4-339 

4-223 

According  to  the  Board  of  Trade,  the  strength  of 
copper  pipe,  well  made,  with  brazed  joints,  is,  work- 

1.  T-  J       T\ 

,  where  T  and  D  are 


6OOO      (T    - 

mg  pressure  =  -         ^ 


the  thickness  and  diameter  in  inches.  If  solid  drawn 
and  not  over  8  inches  diameter,  the  iVmch  is  re- 
placed by  sV-inch. 

Wrought  iron  lapwelded  pipes  of  good  material 
6000  x  T 


are  allowed 


D 


=  working  pressure. 


It  is  well  when  pipes  are  screwed  into  their  flanges 
to  taper  the  hole  on  the  face  side  of  the  flange  and 
roll  over  the  pipe  end.  This  provides  an  extra 
longitudinal  strength.  Pipes  too  thin  in  relation 
to  their  diameters,  if  exposed  to  heavy  end  pull,  will 
jump  clean  out  of  their  sockets  without  showing 
any  injury  to  threads.  They  cannot  do  this  so  well 

74 


STRENGTH    OF    PIPES      • 

with  rigid  flanges,  but  too  much  reliance  must  not 
be  placed  on  mere  screwing. 

Rivets,  again,  must  be  proportioned  for  shear  to 
stand  the  maximum  possible  end  stress  in  the  pipes, 
which  is  not  likely  to  be  greater  than  the  steam  pres- 
sure multiplied  by  the  "  area  of  pipe."  This  "  area 
of  pipe  "  may  be  greater  than  the  nominal  area, 
for  it  is  the  area  enclosed  within  the  joint  ring. 
Rivets  may  be  allowed  a  working  stress  in  shear 
of  10,000  pounds  per  square  inch,  and  will  always 
be  found  to  have  a  large  excess  over  the  stress  on 
even  the  largest  pipes.  Rivets,  therefore,  are  pro- 
portioned for  steam  tightness. 

Longitudinal  rivet  seams,  of  course,  are  propor- 
tioned as  in  boiler  work. 


CHAPTER    VI 
Anti-Priming  Pipes  and  Outlet  Valves 

IT  was  formerly  the  practice  to  lead  off  the  steam 
pipe  from  a  boiler  by  way  of  a  steam  dome. 
But  these  being  found  not  to  abolish  priming  have 
been  discarded,  and  the  steam  pipe  is  attached 
directly  to  a  mounting  block,  which,  as  elsewhere 
stated,  ought  to  taper,  so  as  to  allow  steam  to  enter 
it  without  loss  by  vena  contracta  effect. 

Inside  the  boiler  is  fixed  the  anti-priming  pipe.  This 
is  a  length  of  pipe  which  usually  extends  each  way 
from  the  steam  outlet  block,  into  which  it  is  fitted  by 
a  short  neck  The.  sides  and  top  of  the  pipe  are  slotted 
with  holes,  the  joint  area  of  which  should  be  25  per 
cent,  greater  than  the  area  of  the  steam  pipe  sup- 
plied. Each  branch  of  the  anti-priming  pipe  should 
have  a  diameter  of  about  three-fourths  at  least  of 
the  steam  pipe.  The  anti-priming  pipe  is  held  to 
place  by  hangers  attached  to  riveted  lugs  on  the 
boiler  crown. 

Illustrations  for  ordinary  practice  are  given  in 
Figs.  27  and  28.  It  would  be  good  practice  to 
enlarge  the  central  part  of  pipe  so  that  it  could  be 
brought  down  at  the  bottom,  and  an  easy  leading 

76 


ANTI-PRIMING    PIPES 

curve  made  to  the  outlet,  so  as  not  to  oppose  too 
sudden  a  bend  at  this  point. 

The  holes  in  the  pipe  should  be  confined  to  the 
upper  quarter  or  third  of  the  circumference,  and  it 
is  usual  to  drill  a  drain  hole  at  the  lowest  point  to 
let  out  any  water.  There  ought  properly  to  be  a 
drain  pipe  carried  to  below  water  level  in  order  to 
free  the  drainage  water  from  the  rush  of  steam. 


FIG.    27. ANTI-PRIMING    PIPE    (YATES    &    THOM). 


I 
FIG.    28. ANTI-PRIMING    PIPE    (YATES    &    THOM). 

Anti-priming  pipes  are  made  about  6  feet  long. 
Their  object,  of  course,  is  to  collect  steam  from  a 
considerable  length  of  a  boiler,  so  as  to  avoid  local 
rushes  and  formation  of  vortex  whirls  which  would 
pick  up  water.  They  are  sometimes  made  of  copper 
of  great  length.  The  author  has  seen  them  ex- 
tended to  a  double  or  ring  main  of  over  20  feet  of 
thin  copper,  perforated  or  slit.  This  seems  need- 
lessly long,  for  a  sufficient  spread  of  the  intake  can 

77 


STEAM    PIPES 

usually  be  obtained  in  a  length  of  6  feet,  and  the 
area  of  holes  can  be  got  in  to  the  requisite  extent  of 
1-25  times  the  steam-pipe  area.  If  this  is  exceeded, 
the  steam  will  enter  over  too  limited  a  length  of  the 
anti-priming  pipe  and  defeat  the  object  of  the 
pipe.  It  is  probable  that  excellent  anti-priming 
pipes  could  be  made  from  slitted  brass  sheet  similar 
to  the  slit  brass  used  for  covering  driven  wells,  but 
experiment  is  wanting  to  determine  the  amount  of 
steam  that  will  pass  by  a  given  length  of  slit.  In 
the  water  sheets  the  slits  are  merely  cuts  without 
removal  of  material,  and  are  very  effective  to  keep 
back  sand,  while  passing  water  much  more  freely 
than  it  could  pass  small  holes  of  many  times  the 
area  of  opening. 

THE  STEAM  OUTLET  VALVE. 

These  have  always  been  of  the  mushroom  variety, 
and  have  necessarily  been  opened  with  or  against 
the  pressure  in  the  boiler. 

When  the  valve  opens  against  the  pressure  it  can 
of  course  be  easily  shut,  and  the  pressure  keeps  it 
shut.  It  possesses  the  fatal  objection  that  when 
shut  it  depends  on  the  strength  of  its  spindle  to 
withstand  the  steam  pressure  in  the  main  steam 
pipe,  where  other  boilers  are  at  work.  This  is  a 
fatal  objection,  because  it  endangers  the  safety  of 
the  boiler  cleaner  or  inspector  in  the  idle  boiler. 
The  shut-down  type  has  the  objection  that  in  order 
to  prevent  it  being  opened  when  the  boiler  is  at  rest 
it  must  be  loose  on  its  spindle,  so  that  it  only  opens 

78 


ANTI-PRIMING    PIPES 

by  steam  pressure,  and  these  loose  valves  float  on 
the  outgoing  steam  and  keep  up  a  constant  ringing 
sound,  which,  however,  is  objectionable  only  as 
showing  wear. 

The  author  would  prefer  the  full-way  double- 
faced  slide-valve  type  to  either  of  the  other  two 
forms,  though  this  variety  has  the  fault  that  it  can 
be  opened  during  the  presence  in  the  boiler  of  work- 
men, and  ought  to  be  specially  safeguarded  by  a 
lock. 

The  position  of  the  outlet  valve  is  important.  If 
when  placed  close  to  the  boiler  the  steam  pipe 
extends  vertically  above  the  valve  for  any  distance 
before  bending  away  to  the  main,  or  as  in  some 
cases  the  main  is  immediately  on  the  top  of  the 
vertical  pipe,  then  the  vertical  length  of  pipe 
becomes  a  water  pocket  should  the  boiler  be  at  rest. 
This  necessitates  the  employment  of  a  drain  pipe 
taken  off  the  valve  body  at  the  lowest  point  and 
fitted  with  an  automatic  steam  trap,  for  it  is  too 
dangerous  to  trust  to  the  opening  of  a  drain  cock, 
when  perhaps  a  labourer  is  sent  to  open  up  the 
valve.  The  water  in  the  vertical  pipe  would  all  be 
blown  forward  and  produce  a  most  violent  con- 
cussion at  the  first  square  end,  or  at  the  blank  end 
of  the  main,  or  at  any  interposed  resistance.  Drain 
pipes  and  steam  traps  are  a  source  of  loss  at  any 
time.  Good  practice  eliminates  both  if  possible. 
To  do  this  at  the  stop  valve  the  vertical  pipe  is 
placed  directly  on  the  boiler  block,  and  the  stop 
valve,  if  of  mushroom  type,  is  made  an  angle  valve, 

79 


STEAM    PIPES 

and  placed  at  the  top  of  the  vertical  pipe,  or  if  it  is 
a  slide  valve  it  is  placed  past  the  quarter-bend  which 
follows  the  vertical  pipe. 

Sometimes  there  is  no  vertical  pipe,  but  simply 
a  large  radius  quarter-bend  instead.  In  that  case 
the  stop  valve  comes  next  after  the  bend.  No 
matter  how  placed,  the  broad  principle  to  be  ob- 
tained is  that  the  valve  shall  be  dry,  there  being  a 
fall  each  way  to  the  boiler  and  to  the  engine  or 
steam  main.  This  ensures  freedom  from  water 
disasters,  and  avoids  the  loss  and  annoyance  of 
drains  and  traps.  In  the  course  of  the  nearly  hori- 
zontal pipe  between  the  stop  valve  and  steam  main, 
it  is  a  fairly  common  practice  to  fix  an  automatic 
non-return  valve,  which  is  intended  to  safeguard  a 
boiler  should  it  be  out  of  work.  This  valve  pre- 
vents the  boiler  from  absorbing  steam  from  the 
other  boilers  should  its  pressure  fall  when  cleaning, 
etc.  It  also  prevents  escape  of  steam  should  any 
failure  of  a  boiler  tube  take  place,  and  confines  any 
escape  of  steam  to  the  one  boiler. 

The  idea  of  this  valve  is  excellent,  but  as  usually 
made  with  a  large  rolling  ball  it  is  probable  that  if 
called  on  to  act  suddenly  the  ball  would  shatter 
the  valve  box,  and  the  last  disaster  might  be  worse 
than  the  first.  These  check  or  non-return  valves 
must  be  applied  with  caution. 

In  the  improved  form  made  by  Templer  &  Ranoe 
and  described  in  the  Chapter  on  "  Valves/'  the 
moving  of  a  heavy  weight  through  a  long  distance  is 
avoided. 

80 


ANTI-PRIMING    PIPES 

Danger  may  arise  even  when  a  pipe  is  being 
drained  of  water  preparatory  to  opening  the  steam 
valve,  especially  if  the  water  has  become  cold.  Thus, 
a  horizontal  length  of  pipe  below  a  main  steam  pipe 
may  become  full  of  cold  water,  and  when  partly 
drained  so  that  the  water-level  is  below  the  crown 
of  the  pipe  and  steam  can  enter  above  the  long  hori- 
zontal surface  of  the  water,  there  wil  be  sudden 
condensation  of  some  of  the  steam  ;  waves  will  be 
set  up,  and  inevitably  there  will  be  water  hammer 
and  probably  burst  pipes.1  The  fact  that  a  water 
hammer  takes  -effect  chiefly  at  a  valve,  a  bend,  or  a 
tee  piece,  emphasises  the  badness  of  the  practice 
which  permits  such  valve  bodies  or  tees  to  be  made 
from  cast  iron.  In  laying  out  a  pipe  system,  there- 
fore, the  principle  to  be  observed  is  that  of  a  steady 
progressive  fall  from  the  boiler  stop  valve  to  the 
engine.  In  addition  to  this,  the  question  of  elasticity 
must  also  be  fully  considered.  No  absolute  fixed 
plan  can  be  given,  because  the  system  must  be  varied 
to  fit  the  boilers  and  their  position  relative  to  the 
engine  In  a  bank  of  Lancashire  boilers,  when 
the  steam  outlet  is  central,  the  valve  is  sometimes 
placed  directly  upon  the  mounting  block,  and  the 
steam  branch  curves  out  from  one  side  by  a  quarter- 
round  bend,  and  thence  proceeds  to  the  rear  of  the 
boiler  at  a  height  but  little  above  the  crown  of  the 
boiler,  avoiding  the  manhole  because  of  the  lateral 

1  See  Manchester  Steam  Users'  Association.    Memorandum  by 
Chief  Engineer,  June,  1901. 

Si  G 


STEAM    PIPES 

bend.  Without  this  bend  the  pipe  would  be  in- 
conveniently close  to  the  manhole  cover,  and  for 
this  case  the  vertical  branch  is  employed,  the  valve 
being  high  up  and  upside  down  (see  p.  120).  The 
horizontal  branch  connects  to  the  steam  main,  which 
is  supported  by  hangers,  or  by  brackets,  on  the  rear 
wall.  The  branch  pipes  from  the  boilers  may  enter 
on  the  side  of  the  main,  or  by  a  downward  bend. 
The  length  of  these  branches,  often  15  to  20  feet, 
combined  with  the  length  of  the  vertical  pipe, 
suffice  to  afford  sufficient  elasticity  to  take  up 
stresses  of  expansion. 

Ranges  of  Lancashire  boilers  have  frequently  been 
fitted  with  steam  main  closely  attached  to  the  side 
outlets  of  the  stop  valves.  This  is  an  arrangement 
which  provides  too  little  elasticity  and  is  not  at  all 
to  be  considered,  especially  for  high  pressures  and 
temperatures. 


T 


CHAPTER    VII 
Pipe    Joints 

HERE  are  a  wide  variety  of  means  of  connect- 
ing pipes,  though  these  may  be  classed  under 
three  main  headings,  as  follows  :— 

:i 

(1)  Spigot   and   Socket. 

(2)  Screwed  and  socketed,  or  flush- jointed. 

(3)  Flanged. 

The  first  named  is  named  only  to  condemn  the 
spigot- joint  as  unsafe  for  steam  or  hot  water.  It 
will  draw  apart  should  its  supports  fail,  and  should 
not  be  used. 

The  second  class  is  only  to  be  used  with  sockets, 
and  not  in  the  flush-jointed  form.  It  has  been 
sufficiently  referred  to  under  the  head  of  "  Steel 
Pipes." 

The  third  class  is  found  in  many  forms.  Flanges 
are — 

(a)  Cast  with  the  pipes,  whether  these  are  cast 
iron,  cast  steel  or  cast  malleable. 

83 


STEAM    PIPES 

(&)  Welded  on  to  mild  steel  or  wrought-iron  pipes. 

(c)  Screwed  on  to  mild  steel  or  wrought  iron  and 
sometimes  partly  brazed  in  addition. 

(cF)  Riveted  on  to  mild  steel  or  wrought  iron  or 
copper. 

(e)  Brazed  on  to  copper  pipes. 

(/)  Loose  upon  the  pipes,  which  are  gripped  to- 
gether by  lips  turned  up  on  the  ends  of  the  pipes 
after  the  flanges  are  slipped  on. 

Classes  (a)  to  (e)  are  referred  to  sufficiently  under 
other  headings,  except  as  regards  dimensions  of 
flanges. 

Class  (/)  are  loo  numerous  fully  to  describe.  A 
large  number  will  be  found  illustrated  in  a  paper 
read  by  Mr.  R.  E.  Atkinson.1  Essentially  the  loose 
flange  joint  is  formed  by  slipping  a  flange  over  the 
pipe,  which  is  afterwards  turned  outwards  to  form 
a  lip  or  small  flange,  or  a  thick  ring  flange  is  welded 
on  to  the  pipe  ends. 

Sometimes  each  pipe  end,  if  of  copper,  is  flared 
out  to  an  approximate  quarter-sphere,  and  the 
loose  flanges  draw  the  two  ends  upon  a  solid  interior 
joint  ring,  the  outer  face  of  which  is  an  approximate 
half-circle  and  is  turned  with  circumferential  V- 
grooves,  into  which  the  copper  pipe  is  forced  by 
the  flange  pressure. 

Copper  pipes  are  perhaps  more  suitable  than 
steel  for  loose  flanges,  especially  in  small  sizes. 
Thus  the  2-inch  solid-drawn  copper  water-control 

1  Minutes  of  Proceedings,  Inst.  M.E.,  1901,  page  443. 


PIPE    JOINTS 

pipes  of  the  Cruse  Controllable  Superheater  (Fig.  15) 
are  joined  into  a  continuous  spiral  by  loose  thick 
stamped  steel  flanges,  slipped  loose  on  to  each  end 
of  the  U-pipe.  The  end  is  turned  over  to  form  a 
narrow  flange,  and  this  flange  is  drawn  up  to  the 
face  of  the  connecting  link,  the  copper  itself 
forming  the  metal  to  metal  joint  under  the  heavy 
bolt  pressure.  For  various  forms  of  loose  flange 
joints  the  lists  of  the  Mannesmann  Co.  may  be 
consulted. 

To  secure  steam  tightness  between  flanges  various 
expedients  are  resorted  to. 

The  Manchester  Steam  Users'  Association 
recommend  faced  flanges  with  merely  a  little  red 
paint. 

Oiled  brown  paper  is  sometimes  used  on  faced 
joints. 

Mr.  Dewrance  recommends  scraped  surfaces  for 
pressures  of  350  pounds,  such  as  he  used. 

Ordinary  good  practice  uses  woodite  rings  with 
flat-faced  flanges. 

The  Babccck  Co.  use  the  corrugated  copper 
gasket,  the  flanges  having  a  projecting  face  to  take 
the  rings. 

Compound  rings  of  copper  and  asbestos  have 
considerable  elasticity,  and  make  good  joints.  The 
author  recommends  solid  rings  of  copper  wire,  and 
has  used  ordinary  rV-inch  copper  wire  with  the  ends 
simply  crossed  to  form  a  joint  ring.  What  is  wanted 
to  secure  sound  work  is  a  truly  faced  flange  free 
from  spongy  metal,  and  a  closely  pitched  circle  of 

85 


STEAM    PIPES 

stout  bolts  in  a  strong  flange  so  as  to  ensure  a  tight 
nip  on  the  copper  wire.  If  pipes  are  pulled  apart 
at  any  time,  the  old  rings  must  not  be  put  up  again 
unless  they  are  first  heated  to  a  dull  red  heat  and 
dropped  into  water  to  soften  them,  but  old  rings 
become  flattened,  and  it  is  better  not  to  practise 
such  economies  unless  the  flattened  rings  can  be 
turned  on  edge  to  present  their  long  axes  to  the 
flanges. 

Solid  copper  rings  are  made  in  the  form  of  two 
flat  V's  placed  back  to  back  with  the  idea  that 
the  sharp  edges  of  the  V-grooves  will  make  a 
good  joint ;  but  as  round  copper  wire  is  safe  and 
reliable,  there  seems  no  good  reason  to  seek  further 
complexity. 

Superheated  steam  obviously  demands  that 
nothing  of  an  organic  nature  shall  enter  into  the 
composition  of  a  joint  ring,  for  the  temperature 
will  soon  carbonize  it. 

Where  flanges  are  weak  a  joint  covering  the  whole 
surface  must  be  employed,  or  the  flange  may  break 
when  the  bolts  are  tightened  up.  Flanges  as  shown 
in  Figs,  n,  12,  14,  16  must  therefore  be  strong  and 
stout,  to  withstand  the  bolt  stress,  and  when  a  joint 
is  made  with  a  simple  ring  of  copper  wire  it  should 
not  be  attempted  to  use  a  light  flange.  If  the  flange 
is  light  the  wire  should  not  be  too  far  inside  the  bolts, 
though  too  large  a  ring  of  copper  means  that  more 
pressure  is  required  to  squeeze  the  ring  to  a  tight 
joint. 

For  superheated  steam,  if  not  too  high  in  tempera- 

86 


PIPE    JOINTS 

ture,  Mr.  Vanning  has  found  Jenkins'  graphited 
sheet  to  stand  well.  Probably  asbestos  paper 
rubbed  in  graphite  would  make  a  good  joint  over  a 
fully-faced  flange.  The  graphite  would  prevent 
the  ring  from  sticking  to  the  metal. 

Mr.  Venning  has  used  Rainbow  packing  for  inser- 
tion between  faced  flanges  up  to  180  pounds  in 
several  of  the  largest  power  stations  in  England. 


CHAPTER    VIII 
Supports 

(IPES  may  be  variously  supported,  as  follows 
(i)  By  pillars  from  below,  as  in  Fig.  29. 


FIG.    29. PIPE. PILLAR    AND    SUSPENDER    (YATES    &    THOM). 


(2)  By  hangers  from  above,  as  in  Figs.  29,  30,  31, 


32- 


88 


PIPE    SUPPORTS 

(3)  By  brackets  on  which  the  pipe  rests  (Fig.  33), 
which  shows  simply  the  cross-section  of  a  bracket 


FIG.    30. PIPE    SUSPENDER    (BRITISH    ELECTRIC    TRACTION    CO.] 


of  the  form  of  Fig.  31  carrying  the  pipe  on  its  upper 
,  able. 

89 


STEAM    PIPES 

(4)  On  brick  piers. 

In  the  pillar  form  (Fig.  29),  which  is  convenient 
for  carrying  pipes  from  the  crown  of  a  boiler  or 
from  the  brick  walls  of  the  seating,  the  slightness  of 
the  pillar  affords  play  for  expansion  movements. 
The  head  of  the  pillar  is  arranged  with  an  adjustable 


FIG.    31. SUSPENDER  FOR   ONE 

PIPE  (BABCOCK  &  WILCOX  co.). 


FIG.    32. SUSPENDER    FOR    TWO 

PIPES  (BABCOCK  &  WILCOX  co.). 


screw  to  enable  the  weight  of  the  pipe  to  be  carried 
without  either  undue  upward  or  downward  stress 
on  the  connections  of  branching  pipes.  The  part  on 
which  the  pipe  rests  is  a  bow  of  about  90°  arc, 
to  which  the  pipe  must  not  be  tied  down  unless 
the  bow  is  merely  fitted  into  the  pillar  by  a  tail 
free  to  move  up  in  case  of  the  pipe  rising  from 
expansion. 

Fig.  29  shows  also  the  suspender  of  Messrs.  Yates 

90 


PIPE    SUPPORTS 

&  Thorn,  which  may  be  slung  as  shown  from  a  wall 
bracket  or  from  an  overhead  girder.  The  upper 
nut  may  have  a  helical  spring  placed  between  it  and 
the  bracket.  When  adjusting  any  form  of  pipe 
carrier  with  branches,  the  latter  may  be  unbolted 
from  the  main  pipe  and  their  weight  carried  by  a 
rope  and  balance  weight  equal  to  half  the  weight 
of  the  supported  pipe  if  this  is  fastened  to  the  rope 
near  one  end.  The  main  pipe  is  then  adjusted  to 
height  and  the  branches  bolted  to  it.  A  little  up- 
ward stress  may  be  given  when  cold,  as  this  will  be 
relieved  when  hot  by  the  expansion  of  the  vertical 
branch  on  the  boiler,  if  present.  Suspended  pipes 
are  as  free  to  move  as  their  various  attachments 
will  permit.  Often  they  will  be  set  swinging  or 
vibrating  by  the  pulsating  action  of  the  draught 
of  steam  by  the  engines.  This  is  usually  best  at- 
tended to  after  setting  to  work.  It  may  usually 
be  checked  by  lightly  wedging  the  pipe  at  a 
point  where  one  of  the  branch  pipes  passes 
through  the  wall.  If  the  wedge  only  stops  the 
full  amplitude  of  the  vibration,  this  may  usually 
be  entirely  stopped. 

When  pipes  are  simply  supported  on  brackets 
they  will  not  vibrate  so  readily. 

Brackets  are  often  hollowed  to  the  curve  of  the 
pipe,  but  this  is  a  doubtful  advantage,  tending  to 
prevent  lateral  movement  under  the  push  of  the 
branch  pipes. 

It  is  better  to  provide  the  table  of  the  bracket 
quite  flat  and  plain.  Riveted  to  the  pipe  or  fastened 

01 


STEAM    PIPES 

by  a  pair  of  clip-rings  encircling  the  pipe,  there 
should  be  a  rubbing  piece  of  iron  interposed  between 
the  pipe  body  and  the  bracket  to  take  up  the  wear 
due  to  constant  movement.  These  rubbing  pieces 
should  be  from  f  to  f-inch  thick.  If  a  pipe  is  to  be 
anchored  at  any  bracket  the  rubbing  piece  may  be 
as  per  Fig.  33,  with  down  projecting  pieces  straddl'ng 
the  bracket  table  loosely,  and  with  lateral  extensions 
a  a  to  take  the  clips  c  c  firmly  holding  the  rubbing 
piece  to  the  pipe.  The  encircling  clips  are  in  halves, 
the  bolted  ears  being  placed  at  a  convenient  angle, 
preferably  horizontally. 


FIG.    33- PIPE    BRACKET. 


Pipe  supports  are  intended  only  to  carry  weights 
and  should  not  be  arranged  to  prevent  free  move- 
ment necessary  to  relieve  the  expansion  stresses, 
except  of  course  at  such  point  as  is  intentionally 
selected  as  an  anchorage.  In  the  type  of  hanger 
of  Fig.  30,  with  girder  and  wr ought-iron  rods  and 
clips,  the  girder  is  simply  a  piece  of  4^"  x  2%" 
channel  built  into  the  wall,  and  the  pipe  is  carried  by 
a  saddle  slung  by  a  double-ended  nutted  suspender, 
slung  over  a  pin  carried  on  the  girder.  This  is  the 
design  of  the  British  Electric  Tracjtion  Co.,  and  the 
dimensions  are  given  in  the  accompanying  table. 

92 


PIPE    SUPPORTS 


TABLE    XVII. 

TABLE  OF  DIMENSIONS  OF  PIPE  SUSPENDER  (Fio.  30) 
FOR  STEAM  AND  LAGGED  PIPES. 


Dia. 
of 
Pipe. 

External 
Dia.  of 

r 

Length  of 
Channel. 

Size  of  Strap. 

Dia.  and  Length  of  Sling. 

B 

Bi 

B2 

C 

D 

E 

F 

G 

H 

J 

K 

L 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

i". 

in. 

in. 

in. 

in. 

2 

2i 

IO 

8 

4 

8i 

f 

£ 

Ii 

6 

2i 

£ 

¥ 

13 

3 

3i 

10 

8 

4 

9i 

1 

\ 

Ii 

7i 

2i 

£ 

| 

14 

4 

4i 

12 

9 

4 

ioi 

I 

ft 

¥ 

If 

18 

2* 

-| 

I 

14 

5 

5f 

12 

10 

5 

ni 

I 

g 

20 

2f- 

-| 

I 

16 

6 

6f 

12 

IO 

5 

I2i 

I 

-| 

2 

22i 

3 

¥ 

Ji 

18 

7 

7l 

12 

12 

5 

i3i 

ii 

f 

2 

24 

3 

1 

ii 

19 

8 

8| 

14 

12 

5 

14 

ii 

f 

2 

25 

3 

f 

Ji 

20 

9 

9f 

14 

13 

5 

IS* 

ii 

* 

2 

25 

3 

1 

ii 

20 

FOR  EXHAUST  AND  BARE  PIPES. 


Dia. 

External 
Dia.  of 

Length  of 
Channel. 

Size  of  Strap. 

Dia.  and  Length  of  Sling. 

Pipe. 

Pipe 
A 

B 

Bi 

B2 

C 

D 

E 

F 

G 

H 

J 

K 

L 

in. 
3 

in. 

3i 

in. 
IO 

in. 

8 

in. 
4 

in. 

5i 

in. 
1 

in. 
i 

in. 
Ii 

in. 

in. 

in. 
i 

in. 
i 

in. 
12 

4 

5 

12 

9 

4 

6| 

I 

1 

J4 

I5t 

2i 

f 

£ 

12 

5 

6 

12 

IO 

5 

8 

I 

f 

If 

18 

3 

1 

i 

14 

6 

7 

12 

10 

5 

9 

I 

f 

2 

20^- 

3 

1 

xi 

16 

7 

8* 

12 

12 

5 

10* 

ii 

| 

2 

21 

3 

1 

ii 

16 

8 

9i 

14 

12 

5 

Hi 

ii 

f 

2 

22 

3 

I 

i| 

17 

9 

io| 

14 

12 

5 

I2i 

Ji 

* 

2 

22* 

3 

1 

2 

17 

10 

iii 

14 

15 

6 

14 

i| 

1 

2 

24 

3 

I 

2i 

18 

ii 

12* 

IS 

15 

6 

I4| 

ii 

I 

2i 

24i 

3 

I 

2i 

18 

12 

18 

17 

6 

16 

ii 

I 

2i 

27 

3 

I 

2| 

20 

13 

J4i 

18 

18 

6 

J7i 

ii 

I 

2i 

30 

3i 

I 

3 

22 

14 

is* 

18 

19 

6 

19 

ii 

I 

2i 

30 

3i 

1 

3* 

22 

93 


STEAM    PIPES 

The  resting  of  pipes  on  rollers  carried  by  brackets 
is  not  usually  thought  so  good  as  the  plain  rubbing 
contact  which  introduces  an  element  of  stability 
against  vibration ;  but  after  all,  the  roller-carried 
pipe  is  less  liable  to  vibrate  than  is  the  slung  pipe. 
Rollers  are,  however,  liable  to  become  set  fast, 
and  they  are  then  liable  to  wear  the  pipes  which 
have  not  perhaps  been  supplied  with  rubbing 
pieces. 

In  the  type  of  bracket  of  Fig.  29  there  should  be  a 
projecting  lug  at  the  bottom  of  the  wall  plate  to  rest 
in  the  wall  for  the  purpose  of  taking  the  weight. 
The  two  top  bolts  must  be  strong  enough  to  carry 
the  load  acting  with  an  intensity  of  pull  on  the  bolts 

W  x  A 
S  = ^ — ,  where  N  is  the  distance  between  the 

top  bolt  and  bottom  of  the  bracket  and  A  is  the 
distance  frcm  the  wall  to  the  pipe  centre,  W  being 
the  weight  of  pipe.  The  heads  of  the  bolts  must 
be  carried  by  back  plates,  which  may  be  either 
simple  double-hole  washers,  or  a  full  plate,  as  large 
as  the  wall  back  of  the  bracket. 

The  Babccck  Go.  make  brackets,  as  in  Figs.  31,  32, 
the  dimensions  and  weights  of  which  are  given  in  the 
annexed  Table  XVIII.  Brackets  of  plain  bent  angle 
iron  with  a  riveted  jib  piece  of  flat  iron,  are  made 
with  the  dimension  A  reduced  to  about  half  the 
length,  and  B  and  C  to  less  than  half  for  small 
pipes,  and  to  three-fifths  for  larger  pipes,  and 
they  weigh  less  than  a  third  of  the  cast-iron 
brackets. 

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95 


STEAM    PIPES 

Pipes  may  be  carried  by  simple  projecting  girders, 
similar  to  that  shown  in  Fig.  30,  the  pipe  being 
fitted  with  rubbing  pieces,  as  in  Fig.  33,  and  where 
required  with  anchor-plate  also,  as  in  Fig.  33. 


CHAPTER    IX 
Erection   of  Pipes 

IT  is  very  usual  in  putting  up  a  system  of  pipes 
to  leave  certain  gaps  to  be  filled  on  completion 
with  making-up  lengths.     These  usually  cause  delay 
in  completing  a  piece  of  work. 

Carefully  set-out  work,  erected  to  exact  dimen- 
sions, as  it  may  be,  may  have  all  piping  ordered 
from  the  start,  so  as  to  fit  without  making-up 
lengths. 

In  either  case,  if  the  pipes  are  to  have  an  initial 
stress  when  cold  equal  and  opposite  to  their  stress 
when  hot,  due  allowance  must  be  made  to  meet 
this  requirement,  and  the  final  bolting-up  of  the 
last  piece  will  be  easier  effected  after  steam  has  been 
got  up  and  the  pipes  blown  through  and  heated, 
which  may  be  done  by  blanking  the  ends  still  open 
and  letting  in  full  pressure,  with  due  regard  to  un- 
balanced stresses.  When  the  last  pipe  is  difficult  to 
complete  and  it  is  obvious  that  when  hot  the  cold 
stresses  will  be  relieved  more  or  less,  it  is  desirable 
to  loosen  out  several  flanges  so  as  to  distribute  the 
final  gap  among  several  flanges,  which  are  to  be  all 
screwed  up  together  a  little  at  a  time. 

It  will  sometimes  happen  that  the  final  pipe  does 

97  H 


STEAM    PIPES 

not  present  its  flange  parallel  with  its  fellow.  This 
fault  will  probably  not  be  remedied  when  at  work- 
ing temperature.  It  may  be  treated  drastically  by 
building  round  it  in  place  a  coke  or  charcoal  fire 
in  a  fire-basket,  so  as  to  heat  the  pipe  over  a  length 
of  three  or  four  feet.  While  hot  the  flanges  may 
be  tightened  up  and  the  pipe  will  take  a  set,  and 
should  be  left  to  cool  slowly,  filling  the  fire  with 
lime  or  wood  ashes  to  ensure  this. 

This  fault  of  non-parallelism  of  flanges  is  often 
due  to  faulty  methods  of  templet  making. 

A  pipe  templet  consists  of  a  flat  board,  to  which 
are  attached  wooden  flanges.  The  wooden  flanges 
are  fixed  to  the  ends  of  the  pipes  to  be  joined  up, 
and  the  board  between  is  then  screwed  firmly  solid, 
care  being  taken  that  no  stress  is  set  up.  When 
released  the  flanges  should  fit  the  flanges  they  are 
to  meet  when  finally  cast.  Usually  this  templet 
is  sent  to  the  foundry.  This  is  a  mistake.  It  should 
be  kept,  and  a  second  templet  made  from  it,  but 
reversed,  should  be  sent  to  the  founder. 

Thus  Fig.  34  shows  the  first  templet.  To  this  is 
fitted  the  second,  Fig.  35.  The  flanges  of  this  latter 
are  then  convenient  against  which  to  fix  the  flange 
patterns  in  the  sand.  This  cannot  be  done  with 
the  first  templet  of  Fig.  34,  and  the  use  of  the  second 
templet  ensures  more  accurate  make-up  lengths 
than  can  be  got  by  the  usual  method. 

Similar  templets  must  be  made  to  send  to  the 
steel  pipe  makers. 

For  cast  pipes  the  first  templet  must  be  made  up 

98 


ERECTION    OF    PIPES 

in  length  by  an  amount  equal  to  the  contraction  of 
the  casting,  plus  the  amount  lost  in  facing,  less  the 
joint  rings  and  the  gap  for  initial  stress.  Usually 
the  templet  as  made  will  produce  a  pipe  quite  as 
long  as  will  more  than  fill  the  length  when  at  work- 
ing temperature.  These  matters  must  be  decided 
before  making  the  templet,  and  if  the  final  pipe  is 
to  be  shorter  than  the  above  will  produce,  the  gap 


FIGS.    34,    35. TEMPLETS    FOR    PIPES. 


to  be  filled  can  first  be  shortened  by  a  parallel  blank 
wooden  flange. 

Every  endeavour  should  be  made  to  avoid  the 
final  necessity  of  preparing  a  taper  joint  ring  to  fill 
the  taper  gap  of  non-parallel  flanges,  and  where 
possible  works  must  be  set  out  correctly  and  erected 
to  plan,  so  that  the  pipes  can  be  ordered  from  the 
first. 

This  demands  correct  work  on  the  part  of  the 

99 


STEAM    PIPES 

engine  builder  and  the  fixing  of  a  datum  or  refer- 
ence line  as  between  the  engine  and  boiler  depart- 
ment, so  that  the  two  contractors  cannot  shirk  the 
responsibility.  By  some  it  is  thought  to  be  im- 
possible to  measure  up  for  pipes  correctly  or  to  set 
up  engines  and  boilers  so  that  the  pipes  made  to 
drawing  will  come  into  place,  but  with  care  this  can 
be  done. 


ADDING  TO  EXISTING  PIPE  SYSTEMS. 

It  is  sometimes  desirable  to  add  a  branch  line  to 
an  existing  pipe  system  with  a  minimum  of  stoppage. 
This  can  be  done  without  taking  out  any  existing 
pipe  for  the  purpose  of  putting  in  a  junction  tee. 
Instead  of  this  a  saddle  is  prepared,  as  shown  in 
Fig.  36,  which  fits  upon  the  pipe.  This  saddle  is 
jointed  by  insertion,  or  other  suitable  material, 
according  to  the  pressure,  and  is  gripped  upon  the 
pipe  either  by  a  similar  flanged  saddle  and  bolts  or 
by  strong  U-bolts,  with  nuts  on  the  saddle  flanges. 
After  the  saddle  is  firmly  fixed  and  provided  with 
a  shut-off  valve  that  can  be  quickly  bolted  up,  the 
pipe  may  be  emptied  of  steam,  and  an  opening  cut 
in  it  by  a  drill,  or  a  leading  drill  followed  by  a  crown^ 
cutter.  This  done  the  valve  is  bolted  on,  steam 
admitted,  and  any  residual  cuttings  blown  out 
through  the  valve.  Where  it  is  not  possible  to  shut 
steam  off  for  even  the  short  period  indicated,  the 
valve  must  be  of  the  fullway  type,  blank  flanged 
with  a  special  stuffing  gland-head,  through  which 

TOO 


ERECTION    OF    PIPES 


10 1 


STEAM    PIPES 

works  the  spindle  of  the  drill  and  cutter.  In  this 
case  a  small  valve  ought  to  be  fitted  to  the  body 
of  the  shut-off  valve,  through  which  the  cuttings 
of  the  drill  can  be  discharged  as  the  work  proceeds. 
The  continuous  flow  of  steam  will  prevent  any  cut- 
tings from  falling  into  the  main  steam  pipe  and  will 
keep  the  cut-out  disc  upon  the  leading  drill,  so  that 
on  completion  of  the  cut  the  disc  can  be  drawn  back 
through  the  valve,  the  valve  closed  and  the  drilling 
fixture  removed.  The  author  is  indebted  to  Mr.  A. 
Venning  for  this  saddle  connection.  When  the  con- 
ditions permit  of  it  the  hole  cut  through  the  pipe 
may  be  merely  a  number  of  drilled  holes  arranged 
so  as  to  leave  a  portion  of  solid  plate,  though  it  will 
be  observed  that  the  saddle  itself  acts  as  a  rein- 
forcement of  the  weakened  pipe,  and  that  any 
weakening  is  upon  so  short  a  length  as  to  be  of  little 
account.  Still  it  should  be  considered,  and  if  neces- 
sary provided  against. 

Before  proceeding  to  erect  pipes,  all  the  bolts 
should  be  cleaned  by  boiling  in  soda,  oiled,  and  the 
nuts  run  over  until  they  can  be  turned  with  the 
fingers.  As  each  pipe  is  put  in  place  it  should  only 
be  loosely  bolted,  using  a  short  spanner  easily. 
Steam  should  be  sent  through  to  heat  up  the  pipes, 
and  all  bolts  gradually  and  in  turn  tightened  up, 
first  with  medium  spanner,  or  spanners  held  at  half- 
length,  and  finally  with  full-length  spanner.  The 
steam  pressure  should  be  only  a  pound  or  two  above 
atmosphere  during  this  work.  If  any  joints  leak 
when  steam  is  got  up  to  full  pressure,  they  should 

102 


ERECTION    OF    PIPES 

be  marked  and  attended  to  after  pressure  is  shut  off. 
The  risk  of  leakage  will  be  minimized  by  the  gradual 
method  outlined  above. 

Pipes  of  small  size  may  be  bent  cold,  but  a  better 
job  is  usually  made  by  heating  to  a  clear  red  and 
bending  round  pins  fixed  on  a  bench  or  in  the  vice. 
A  good  workman  will  often  bend  an  empty  pipe 
without  spoiling  its  circularity  by  coaxing  it  in  the 
vice,  with  which  he  squeezes  it  laterally  and  pre- 
vents it  taking  an  oval  section  round  the  bend. 
Less  experienced  men  should  fill  the  pipe  with  sand, 
thoroughly  dried,  to  prevent  explosion  by  steam. 
Such  a  filled  pipe  will  remain  truly  circular  when 
bent,  and  the  sand  will  drop  out  as  soon  as  the  end 
plugs,  which  retain  it,  are  removed.     Copper  pipes 
may  be  filled  with  melted  resin,  which  when  cooled 
will  enable  the  pipe  to  bend  without  crippling,  the 
resin  being  plastic-brittle,  and  crushing  round  the 
bend  with   expansive   effect.     The   resin   must  be 
melted  out.     Or  pipes  are  filled  with  melted  solder 
or  other  alloy  of  low  melting  point.     Water  or  oil 
would  probably  serve  if  the  ends  could  be  kept  tight. 
The  theory  of  bending  by  using  a  filling  is  of  course 
that  a  circle  contains  the  maximum  area  of  cross- 
section  for  a  given  periphery,  and  any  change  from 
a  true  circle  would  have  to  compress  the  filling 
material.     It  is  easier  for  the  pipe  to  maintain  its 
full  circle.     An  unfilled  pipe  is  apt  to  cripple  on  the 
inside  of  the  bend,  or  to  flatten  on  the  outside.    Iron 
or  steel  pipes  can  always  be  made  sufficiently  hot 
by  laying  them  in  a  long  brick  trough  built  up  of 

103 


STEAM    PIPES 

loose  bricks,  with  air  spaces  and  with  space  under 
the  pipe  for  fire.  Wood  or  coal  can  be  used  as  fuel. 
The  acquisition  of  the  clear  red  temperature  can 
best  be  judged  in  an  unfilled  pipe  by  looking  through 
it  as  it  lies  in  the  fire.  Above  four  inches  pipes 
can  rarely  be  bent  or  shaped  except  by  pipe  makers. 


I  04 


CHAPTER    X 
General  Arrangements 

THE    general    arrangement  of  a  modern  power 
station  demands  that  the  steam  pipes  enter 
into  consideration  as  a  prime  factor,  and  not  as  an 
after-thought.     This  is  especially  the  case  where 
superheat  is  to  be  employed. 

The  common  arrangement  of  a  long  row  of  boilers 
separated  from  a  long  row  of  engines  by  a  wall, 
with  sometimes  a  steam  main  on  each  side  of  the 
wall,  is  by  no  means  good.  Ring  mains  are  bad 
practice,  yet  in  such  a  design  it  becomes  almost 
imperative  to  adopt  a  form  of  ring  main  if  separately 
fired  superheaters  are  to  be  employed,  for  steam 
must  be  led  to  the  superheater  from  all  the  boilers 
in  a  section,  and  from  the  superheater  to  the  engine 
main.  In  the  face-to-face  arrangement  of  boilers  such 
as  was  adopted  for  the  Central  London  Railway  or 
the  L.C.C.  Station  at  Greenwich,  the  placing  of  a 
separately  fired  superheater  almost  compels  a  ring 
main,  and  such  stations  are  examples  of  an  unfortu- 
nate shape  of  the  plot  of  land  on  which  they  are 
built.  With  steam  turbines  capable  of  using  more 

105 


STEAM  PIPES 

steam  in  a  given  length  of  engine  room,  the  disposi- 
tion of  boilers  must  be  along  a  line  at  right  angles 
to  the  engine  room,  i.e.  each  boiler  is  parallel  with 
the  length  of  the  engine  room,  and  the  bank  of 
boilers  is  transverse  thereto. 

The  number  of  boilers  in  each  bank  will  depend 
upon  the  demands  of  the  engines,  and  usually  would 
be  such  as  are  necessary  to  supply  the  demands 
of  the  engine.  There  is  a  tendency  to  regard  each 
engine  and  its  boilers  as  a  separate  entity. 

This  would  preclude  all  idea  of  steam  mains  other 
than  that  of  coupling  all  the  boilers  in  a  bank  and 
extending  to  the  engine.  Where  it  is  considered 
necessary  to  have  one  engine  at  work  and  another 
moving  slowly  round  in  case  of  mishap,  this  idea 
would  also  imply  a  set  of  boilers  at  work  and  a 
second  set  under  full  pressure  with  banked  fires, 
and  in  a  considerable  installation  this  would  be 
uneconomical,  and  two  adjacent  engines  may  at 
least  be  able  to  draw  steam  from  one  set  of  boilers. 
It  is  certainly  not  good  economy  to  multiply  boilers 
to  the  extent  that  the  full  carrying  out  of  this  idea 
would  demand.  The  total  boiler  capacity  need 
only  be  more  than  the  mean  demand  for  steam  in 
a  tramway  station  by  the  amount  of  the  necessary 
spares  and  the  number  of  boilers  in  each  bank, 
and  the  number  of  banks  will,  therefore,  depend 
upon  the  total  number  required,  the  length  available 
and  the  superheater  dimensions. 

The  requirements  of  the  superheater  demand 
to  be  considered,  and  if  the  banks  of  boilers  are  placed 

1 06 


GENERAL  ARRANGEMENTS 

at  right  angles  to  the  engine  room  this  enables  the 
separately-fired  superheater  to  be  placed  next  the 
engine-room  wall  between  it  and  the  first  boiler. 
All  the  boilers  turning  their  steam  into  a  main 
pipe  run  across  the  boilers,  this  pipe  is  carried 
directly  forward  to  the  engine  room  with  a  stop  valve 
in  the  longitudinal  centre  line  of  the  superheater.  On 
each  side  of  this  stop  valve  branch  cut  the  pipes 
which  form  a  loop  with  the  superheater.  Each 
end  of  the  loop  has  its  valve  close  to  the  steam 
main,  and  the  engine  may  thus  be  supplied  with 
steam  saturated  or  superheated  by  suitable  opening 
or  closing  of  these  three  valves. 

This  arrangement  minimizes  the  length  of  pipe 
containing  superheated  steam  :  it  affords  the  simplest 
and  most  direct  run  for  the  steam  from  each  boiler 
to  the  engines.  If  a  steam  main  is  wanted  in  the 
engine  room,  it  can  easily  be  arranged  to  take  steam 
from  each  superheater  and  deliver  it  by  branches 
to  the  engines,  but  this  main  should  be  propor- 
tioned rather  as  a  balancer  than  as  a  main  to 
carry  all  the  steam  made  at  any  point  beyond  a 
given  section  to  any  other  point  in  the  opposite 
direction.  If  too  much  is  thought  of  provid- 
ing every  possible  permutation  and  combination 
of  steam  boilers  and  engines,  the  inevitable  result 
will  be  that  an  excessive  diameter  and  cost  of  pipe 
will  be  entailed.  It  is  sounder  practice  to  use 
small  pipes  where  improbable  combinations  are 
to  be  provided  for  and  allow  temporary  loss  of 
pressure  by  wire-drawing,  than  to  charge  standing 

107 


STEAM  PIPES 

expenses  with  the  extra  interest  on  heavy  pipes 
and  the  excessive  cost  of  heat  radiation  losses. 

The  steam  pipe  across  each  bank  of  boilers  may 
for  economy  be  stepped  down  in  diameter  towards 
the  extreme  end.  Where  this  is  done,  and  there  is 
a  prospect  of  extensions  being  made,  it  is  obvious 
that  this  ought  theoretically  to  take  effect  between 
the  superheater  and  the  first  boiler.  The  same 
result  will  be  obtained  by  putting  in  the  new  boiler 
at  the  extreme  outer  end  of  the  bank,  and  putting 
in  a  new  and  perhaps  larger  length  of  steam  pipe 
at  the  opposite  end.  This  points  to  the  necessity 
of  accurately  spacing  all  boilers  alike  and  having 
each  section  of  boiler  main  pipe  of  exact  length, 
so  that  the  boiler  branches  will  fit  the  main  when 
this  is  moved  endwise  a  section  or  two  more.  Usually 
this  will  not  be  the  mode  of  extension,  though  it 
might  follow  the  introduction  of  an  improved 
form  of  turbine.  Should  occasion  demand  it,  each 
boiler  main  pipe  may  be  connected  across  to  the 
pipe  of  the  next  bank  in  order  that  an  excess  of 
superheaters  need  not  be  installed,  but  usually  a 
well-managed  station  can  be  worked  so  as  to  enable 
the  cleaning  of  a  superheater  to  coincide  with  the 
cleaning  of  several  boilers  in  one  bank,  and  the 
virtual  stoppage  of  the  whole  bank. 

This  should  be  aimed  at  by  providing  rather  a 
small  amount  of  first-class  plant  than  an  excess  of 
cheap  trash. 

As  an  illustration  of  the  practice  of  economy  in 
pipe  dimensions,  suppose  for  simplicity  that  half 

1 08 


GENERAL  ARRANGEMENTS 

the  plant  in  a  station  was  spare.  Then  the  worst 
condition  for  the  steam  main  along  a  row  of  engines 
would  be  that  the  whole  of  the  north  engines  were 
supplied  from  the  south  end  boilers,  all  the  south 
engines  and  north  boilers  being  at  rest. 

Suppose  this  demanded  the  middle  of  the  steam 
main  to  have  an  area  of  400  in .  cross-section  to  give 
the  proper  velocity  of  flow  of  steam.  A  good 
practical  solution  with  a  view  to  probability  and 
economy  would  be  first  to  cut  the  area  to  one-half 
on  the  assumption  that  not  more  than  one-half  the 
total  steam  would  be  called  on  to  pass  any  one  point 
in  the  main,  and  secondly  to  reduce  it  still  further 
by  perhaps  20  per  cent,  on  the  assumption  that 
under  conditions  of  such  rare  occurrence  the  velocity 
of  the  steam  might  be  increased  rather  than  that 
the  station  should  carry  a  perpetual  interest  charge 
on  huge  pipes  and  a  heavier  radiation  loss. 

Designers  may  also  consider  the  use  of  reduced 
sizes  of  valves  where  economy  in  cost  is  of  more 
than  usually  serious  moment.  The  resistance  of 
pipes  is  so  much  a  matter  of  length  that  a  short 
piece  of  smaller  size  may  be  permitted,  and  smaller 
valves  of  the  fullway  type  with  conical  ajutage  will 
serve  to  cut  down  expenses. 

Thousands  of  pounds  have  been  wasted  on  exces- 
sive valve  proportions  in  excessive  mains  which  are 
never  called  upon  to  give  other  than  a  balancing 
effect.  One  of  the  evils  of  the  ring  main  is  that  it 
must  be  equally  large  throughout,  for  it  is  only  put 
up  upon  the  assumption  that  it  must  carry  all  the 

109 


STEAM    PIPES 

steam  any  way  round.  It  is  crowded  with  valves, 
supposed  any  one  of  them  capable  of  being  moved 
if  a  mishap  occurs.  Yet  so  little  is  the  design  of  them 
thought  out  that  the  handles  of  the  valves  may  be 
found  carried  up  to  platforms  placed  directly  over 
the  mains,  so  that  should  an  accident  happen  the 
man  who  essays  to  close  the  valves  will  be  scalded 
by  the  steam.  Steam  is  lighter  than  air  in  the 
ratio  of  9  to  15  for  equal  tempera  ure,  and  valves 
should  rather  be  got  at  below  the  level  of  possible 
steam  escape. 

Similarly  in  a  bank  of  eight  boilers,  of  which  there 
will  usually  be  six  at  work,  the  size  of  the  pipe  must 
nowhere  be  larger  than  required  to  carry  steam  from 
six  boilers,  and  this  size  will  extend  from  No.  6  past 
Nos.  7  and  8.  Indeed,  it  is  open  to  argument  that 
the  5-boiler  size  might  be  extended  to  between 
Nos.  6  and  7,  for  it  would  usually  be  contrived  not 
to  have  7  and  8  off  at  the  same  time,  and  only 
steam  from  five  boilers  would  usually  traverse  the 
section  of  pipe  up  to  No.  7.  In  the  odd  event  of 
doing  so,  it  would  be  permissible  to  allow  temporary 
increase  of  velocity  of  the  steam.  Such,  then,  are  the 
principles  affecting  design  where  proper  consideration 
is  given  to  economy  of  coal  and  maintenance  and 
running  expenses,  so  as  to  avoid  rendering  the  cost 
of  connecting  up  the  main  items  of  plant  greater 
than  the  cost  of  the  plant  itself. 

Power-station  designers  should  also  be  prepared 
to  consider  the  question  of  getting  very  much  more 
steam  from  boilers  than  has  hitherto  been  attempted. 

no 


GENERAL  ARRANGEMENTS 

The  author  has  long  advocated  the  use  of  feed 
water  heated  fully  up  to  the  boiler  temperature, 
and  has  adopted  the  conservative  estimate  of  a 
better  output  by  20  per  cent,  as  the  effect  to  be 
expected  from  fully  heating  up  feed  water  in  the 
control  system  of  a  superheater.  Mr.  Cruse  sup- 
ports this  estimate,  but  Col.  Crompton  has  stated 
that  with  such  a  fully  heated  feed  a  water-tube 
boiler  has  evaporated  at  least  double  its  ordinary 
rated  output.  There  is  at  least  evidence  that 
boilers,  badly  worked  as  they  usually  are,  are  in 
excess  of  what  they  need  be  in  better  practice. 

This  question,  however  important  to  the  design 
of  pipes,  is,  however,  too  large  to  be  further  dealt 
with  here.  The  point  has  an  important  bearing, 
however,  on  the  whole  question  of  pipes,  both  in 
general  arrangement  and  in  the  dimension  of  the 
pipes  of  each  individual  boiler. 


CHAPTER    XI 
Valves 

A 

SOME  valves  are  always  necessary  in  the  course 
of  a  steam  pipe,  but  the  number  should  be  a 
minimum.     One   valve    at   least   must    always    be 
applied,  viz.  the  boiler  stop-valve,  the   position  of 
which  has  been  discussed  elsewhere. 

As  with  junction  pieces,  valves  are  exposed  to 
the  stresses  in  a  system  of  pipes,  and  are  often 
made  with  cast-iron  bodies  even  in  a  system  of  steel 
pipes.  Thus  in  Figs.  37  and  38  are  shown  two 
types  of  valves  by  Templer  and  Ranoe,  which  are 
supplied  with  cast-iron  bodies  for  pressures  up  to 
200  Ib.  The  valves  and  seatings  are  of  high  pressure 
bronze,  the  seating  being  fixed  into  the  body  by 
studs,  as  shown,  thus  avoiding  the  warping  of  the 
seat  by  differential  expansion,  such  as  occurs 
where  seats  are  tightly  pressed  into  cast  iron.  The 
joint  is  made  on  the  flange,  and  admits  of  a 
sufficiency  of  movement  to  take  up  expansion. 
Tables  XIX.,  XX.  give  the  leading  dimensions. 

112 


VALVES 

In  these  valves  the  spindle  has  a  head  which 
makes  a  free  turning  joint  on  the  valve.  As  in 
all  good  practice  the  screw  of  the  spindle  is  outside 


FIG.    37. ANGLE    STOP   VALVE    (TEMPLER    &    RANGE). 


and  carried  in  a  cross  bar  with  pillars  on  the  cover. 
The  screw  is  thus  fully  in  sight,  and  can  be  kept 

113  i 


STEAM    PIPES 


FIG.    38. STRAIGHTWAY    STOP    VALVE. 


TABLE    XIX. 

Cast-iron  Bodies  ahd   High-pressure   Bronze  Working  parts  for 
Steam  Pressures  up  to  200  Ib.  per  square  inch. 

RIGHT-ANGLED  PATTERN  (FiG.  37). 


Bore  .     . 

2 

2i 

3 

3J 

4 

5 

6 

7 

8 

g-in. 

Dia.        of 

Flanges 

6i 

7 

8 

i 

9 

IOJ 

12 

13* 

15 

16    „ 

Thickness 

of  Flange 

i 

I 

I* 

It 

ij 

ii 

If 

ii 

if 

if» 

Dimension, 

B     .    . 

4i 

5 

6 

7 

71 

8| 

91 

ioi 

-iii 

12     „ 

Dimension, 

A    .     . 

51 

6i 

7 

7i 

8 

9i 

IO 

ii 

12 

13     » 

Dimension, 

* 

C     .    . 

12 

I2i 

I2| 

i3i 

17 

i8f 

19! 

2li 

22| 

24  „ 

114 


VALVES 

All  high-pressure  gunmetal  for  200  Ib.  pressure. 


Bore     .     .     . 

2 

2} 

vin. 

Dia.  of  Flanges   .   ;  . 

64 

7 

8     „ 

Thickness  ,,     „   .      . 

5 

¥ 

1 

4t« 

Dimension  B  . 

4 

5 

6      „ 

A         .      . 

5 

5t 

51        M 

„         C         .      . 

8i 

IDA 

ii    „ 

TABLE    XX. 
STRAIGHTWAY  PATTERN   (FiG.  38). 

Cast-iron  Bodies  and  High-pressure  Bronze  Working  Parts  for 
Steam  Pressures  up  to  200  Ib.  per  square  inch. 


Bore  .      . 

2 

2* 

3 

3* 

5 

5 

6 

7 

8 

9 

10 

12  in. 

Dia.        of 

Flanges  . 

6*     7 

8 

8J 

9 

10}  12 

i3i 

15 

16 

17  19 

Thickness 

i 

of  Flanges 

i 

I 

i* 

ii|    ii 

i* 

If 

if 

I» 

2    „ 

Length 

over 

Flanges 

10 

IX 

12 

13 

14 

17 

20 

22 

24 

26 

28 

32  „ 

All  high-pressure  gunmetal  for  200  Ib.  pressure. 


Bore 

2 

2* 

3-in. 

Dia.  of  Flanges. 

6* 

7 

8    „ 

Thickness 

i 

1 

13 
1  6   " 

Length  over  Faces    . 

8 

9 

I      „ 

clean  and  lubricated.  Fig.  37  is  suitable  for  a 
boiler  stop-valve  when  placed  directly  on  the 
mounting  block  or  on  the  top  of  a  vertical  branch 
from  that  block.  The  outlet  flange  may  point 
either  longitudinally  along  the  boiler  or  trans- 
versely as  circumstances  demand.  In  the  latter 

115 


STEAM    PIPES 

event  there  is  introduced  a  quarter-bend  between 
the  valve  and  the  straight  branch  to  the  main,  and 
this  may  be  desirable  on  the  score  of  elasticity. 


FIG.    39. FULLWAY  MAIN  VALVE  WITH    BYE -PASS   RELIEF  VALVE. 

The  figures  show  how  the  pillars  should  be  attached 
— not  being  simply  screwed  into  tapped  holes, 
drilled  often  by  error  or  carelessness  through  into 
the  steam  space.  When  used  as  boiler  stop- valves 

116 


VALVES 


there  is  no  difficulty  in  opening  these  valves,  but 
where  valves  are  placed  under  conditions  which 
demand  their  opening  against  the  steam  pressure, 
it  is  usual  in  the  larger  sizes  to  provide  a  smaller 
bye-pass  valve  fixed  to  the  body  of  the  valve  as 


iliiiiilliii 


FIG.    40. — SECTION    OF    "  FULLWAY  "    VALVE. 

in  Fig.  39,  in  order  that  the  pressure  may  be  equal- 
ized on  the  two  sides  of  the  main  valve  before 
opening  it.  The  bye-pass  serves  for  warming- 
through  purposes  also.  Thus  Fig.  39  shows  a 
straightway  stop-valve  with  bye-pass,  and  in  Fig.  40 
the  valve  is  shown  in  section,  and  diagrammatically 
in  Fig.  41—^4  being  the  body  B  the  seat  ring  of 
the  same  material  forced  into  the  body ;  C  the  bronze 
or  nickel  alloy  seat  screwed  into  B  and  making  a 
joint  on  the  flange  ;  D  the  carrier,  which  lifts  or 

TT7 


STEAM    PIPES 


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118 


VALVES 

lowers  the  valve  ;  E  E  the  two  halves  of  the  valves 
carrying  faces  of  bronze  or  nickel  alloy  for  superheat, 
and  F  F  being  the  wedges  which  force  the  valve 
against  their  seat  when  the  spindle  of  the  lower 
wedge  F  touches  the  bottom  of  the  body  casting. 

A  table  of  general  dimensions  of  fullway  valves 
(Fig.  41,)  by  Templer  and  Ranoe  is  given  on  page 
121,  and  will  be  found  fairly  approximate  for  other 
makes  of  valves. 

The  hand  wheel  F  may  be  made  into  a  gear  wheel, 
and  turned  by  a  pinion  with  a  long  spindle  extending 
downwards  within  reach,  in  cases  where  valves  are 
placed  high  and  out  of  reach.  Such  wheels  and 
pinions  ought  to  be  made  with  wide  teeth  for 
strength  as  they  do  not  perhaps  afford  the  same 
power  over  the  valve  as  the  direct  method  of  Fig/ 42 
and  Table  XXII. ;  which,  however,  demands  a  re- 
versed position  of  the  valve  with  the  risk  of  possible 
objectionable  leakage  of  water  at  the  gland.  The 
hand  wheel  of  a  reversed  valve  should  be  attached 
by  a  nutted  screw,  as  the  wheel  may  drop  off  when 
only  keyed. 

VALVE  POSITION. 

Valves  may  sometimes  be  seen  upon  a  ring  main 
with  their  spindles  brought  up  to  a  gallery,  with 
a  grid  floor  placed  directly  over  the  ring  main. 
Obviously,  any  accident  to  the  main  may  envelope 
the  valve  gallery  in  steam  and  render  the  hand- 
wheel  inaccessible.  This  arrangement  is  on  a  par  with 
the  intelligence  which  employs  ring  mains  by  choice. 

119 


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FIG.    42.  — "  FULLWAY  "    VALVE    REVERSED,    WITH    EXTENSION    SPINDLE 

(TABLE  xxn.). 
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122 


VALVES 

ISOLATING  VALVES. 

Isolating  valves  made  with  a  heavy  ball  so  arranged 
as  to  roll  back  to  a  seat  in  event  of  a  rush  of  steam 
towards  the  boiler  to  be  isolated,  are  probably 
dangerous  owing  to  the  momentum  acquired  by  the 
heavy  ball  under  the  pressure  of  the  steam.  Some- 


FIG.    43. ISOLATING    VALVE    (TEMPLER    &    RANGE). 

thing  lighter  is  more  desirable,  and  in  Fig.  43  is 
shown  a  combined  stop  and  isolating  valve  so 
arranged  that  when  the  upper  valve  F  is  open  the 
lower  valve  D  is  raised  about  -33¥-inch  of  its  seat  by 
the  short  spring  C.  When  steam  is  flowing  the 
valve  rises  and  compresses  the  long  spring  G.  If 
the  boiler  pressure  drops  below  that  in  the  pipes 

123 


STEAM    PIPES 

the  difference  of  a  pound  per  square  inch  will  bring 
the  lower  valve  to  less  than  |-inch  from  its  seat,  and 
any  further  reduction  soon  closes  it.  By  this  valve 
a  boiler  at  once  ceases  to  be  fed  from  other  boilers, 
and  should  the  fires  of  any  boiler  get  into  bad 
order  at  a  period  of  demand  for  steam,  this  particular 
boiler  does  not  become  a  drag  on  the  others.  The 
isolating  valve  quite  safeguards  men  inside  a  boiler, 
for  even  if  the  valve  be  "  opened  "  the  lower  valve 
remains  closed,  and  can  only  open  when  full  steam- 
pipe  pressure  again  comes  below  it. 

EXHAUST  VALVES. 

The  valves  in  the  pipes  connecting  each  engine 
to  a  common  exhaust  main  should  always  be  of 
the  full  way  type.  No  bye-pass  is  necessary.  The 
spindle  glands  should  have  a  deep  box  for  stuffing, 
which  should  be  of  a  soft  fibrous  order,  well  lubri- 
cated with  wax.  These  valves  in  exhaust  pipes  are 
doubtless  a  prolific  source  of  air  inlets  when  badly 
attended  to,  and  a  frequent  cause  of  poor  vacuum. 
As  they  are  always  cool  a  fibrous  packing  comes  to 
no  harm. 

It  need  hardly  be  said  that  though  valve  bodies 
are  frequently  made  of  cast  iron  even  for  high  pres- 
sures, and  that  such  castings  when  used  by  a  reput- 
able firm  are  apt  to  be  much  stronger  and  sounder 
than  the  ordinary  run  of  cast-iron  pipe  work,  still  it 
is  safer  to  employ  valves  with  bodies  of  cast  steel, 
especially  where  undue  stresses  can  be  foreseen. 

124 


VALVES 


Very  large  valves  are  made  of  the  equilibrium 
type,  and  require  no  equalizing  bye-passes,  but 
they  have  always  proved  most  difficult  to  maintain 
tight  because  it  is  practically  impossible  to  screw 
down  two  valves  rigidly  upon  two  rigid  seatings 
owing  to  differences  of  expansion.  Some  relief 
might  perhaps  be  secured  by  a  spring  device  on 
that  valve  which  is  helped  to  its  seat  by  the  steam 
pressure.  A  remedy  has  been  attempted  by  making 


FIG.  45. FINAL  FORM 

OF  FLEXIBLE  SEAT 
OF  VALVE. 


FIG.  44. FLEXIBLE  SEAT  VALVE. 

one  of  the  valves  merely  a  balance  piston.  Full 
information  on  the  subject  may  be  ound  in  a  paper 
read  to  the  North-East  Coast  Institution  of  Engineers 
by  Mr.  J.  H.  Gibson  on  December  12,  1902,  vol.  xix., 
in  which  he  described  the  troubles  incidental  to 
double-beat  valves  and  the  stresses  to  be  dealt 
with,  and  finally  the  experiments  with  flexible 
discs  which  resulted  in  the  adoption  of  the  valve 
shown  in  Fig.  44,  one  valve  only  in  a  double-beat 

125 


STEAM    PIPES 

valve  being  fitted  with  the  disc,  the  other  seating 
solidly.  The  disc  provides  for  all  distortion  and 
spindle  expansion,  which  combined,  cause  the  trouble 
in  this  type  of  valve.  In  Fig.  45  is  shown  the  plain 
flat  disc  finally  adopted  in  place  of  the  form  shown 
in  Fig.  44.  It  is  not  possible  in  the  present  work 
to  go  more  fully  into  the  question  of  valves,  which 
are  however  a  sufficiently  important  part  of  a 
steam  pipe  system  to  demand  more  attention  than 
engineers  usually  give  to  them. 

To  effect  the  same  end  as  the  flexible  seat, 
Holden  &  Brooke  have  brought  out  a  double  valve 
in  which  the  two  valves  are  not  attached  to  the 
same  spindle.  Each  valve  has  its  own  independent 
spindle.  These  pass  through  stuffing  boxes  at 
opposite  ends  of  the  casing,  and  are  pinned  to  levers 
with  their  fulcra  on  short  pivoted  links  pinned  on 
to  the  covers.  The  long  end  of  each  lever  projects 
clear  of  the  valve  body  and  carries  a  nut,  in  which 
works  a  right  and  left  screwed  spindle  carrying  the 
hand  wheel.  By  this  contrivance  each  valve  is 
pressed  upon  its  seating  with  equal  force,  and  there 
is  no  possibility  of  one  valve  leaking  while  the  other 
is  tight  by  reason  of  any  differential  expansion, 
such  as  happens  with  large  double-seated  valves 
of  common  type. 

Attention  should  be  directed  to  the  weak  feature 
of  all  globe  valves  as  Fig.  38,  namely,  the  obstruction 
they  offer  to  the  free  flow  of  water  along  a  pipe. 
The  valve  should  shut  against  the  pressure  where 
safe  to  allow  this,  and  there  should  be  a  drain  from 

126 


VALVES 

the  base  of  the  globe  body  steam  flowing  from  the 
left.  Often,  as  in  a  balancing  header,  steam  may 
flow  either  way,  and  two  separate  drains  would  be 
needed.  A  well  designed  fullway  or  gate  valve  is 
preferable.  The  larger  the  valve  the  more  are  the 
faults  of  globe  valves  intensified  and  dangerous. 


127 


CHAPTER    XII 
Drainage 

DRAINAGE  has  already  been  incidentally  re- 
ferred to  in  other  chapters. 

It  is  an  essential  provision  which  is  minimized 
in  a  good  design,  and  a  superfluity  of  drainage 
devices  indicates  faulty  design  :  thus  a  stop  valve 
at  the  bottom  of  a  vertical  p.pe,  as  when  the  boiler 
outlet  valve  is  not  at  the  highest  point  of  a  steam 
range,  causes  water  to  collect  above  the  valve,  and 
this  must  be  drained  away.  If  not  drained  away, 
then  upon  opening  the  steam  outlet  valve  the  body 
of  water  above  the  valve  may  be  shot  forward  like 
a  projectile  to  rupture  the  pipe  at  the  first  obstruction 
or  square  end. 

That  more  accidents  have  not  happened  is  due 
to  the  fact  that  a  boiler  joined  up  to  other  working 
boilers  has  often  its  steam  valve  "  open  "  before 
the  boiler  can  raise  the  valve.  The  valve  only  rises 
as  the  pressure  on  both  sides  of  it  become  slowly 
equal,  and  the  collected  water  falls  quietly  through 
the  open  valve.  The  steam  pipe  ought  to  fall 
gently  all  the  way  to  the  engine,  or  to  some  other 
drainage  point. 

128 


DRAINAGE 

Automatic  steam  traps  are  connected  to  such 
drainage  point  which  remove  the  water  as  this 
collects.  Under  the  term  drainage  is  also  under- 
stood all  those  little  but  important  provisions  for 
giving  a  free  flow  to  water,  such  as  the  little  bridging 
pipes  across  the  lower  parts  of  expansion  bands 
when  these  stand  vertically.  There  must  be  drainage 
to  the  water  separator  next  the  engine,  and  at  any 
point  where  water  can  collect.  In  the  best  design 
there  will  be  one  drain,  viz.  that  at  the  water 
separator  only. 


FIG.    46. — EXPANSION    STEAM    TRAP    (HOLDEN    &    BROOKE). 

Steam  traps  are  very  various  in  make,  depending 
some  on  floats,  some  on  differential  expansion. 
The  one  example  illustrated,  for  this  is  a  book  on 
pipes  rather  than  accessories,  is  the  expansion  trap 
of  Holden  &  Brooke  (Figs.  46-49). 

The  object  of  a  steam  trap  is  to  let  water  escape 
from  a  pipe  without  letting  out  any  steam.  In  a 
form  of  low-pressure  trap  a  valve  is  screwed  to 
and  from  its  seat  by  the  rise  and  fall  of  a  ball 
float.  A  small  leak  allows  the  ball  gradually  to 
fill  and  sink.  It  opens  a  small  valve  when  it 
sinks,  and  this  admits  water  from  the  pipe  to  be 
drained.  This  water  further  fills  up  the  ball,  and 

129  K 


STEAM    PIPES 

overflows  by  an  inverted  syphon  from  the  upper 
side  of  the  ball.  The  following  steam  blows  out  the 
whole  of  the  water  from  the  pipe,  and  finally  blows 
out  that  in  the  ball  itself,  which  promptly  floats  up 
and  closes  the  escape  valve  until  such  time  as  the 
small  leak  into  the  ball  sinks  it  again  and  re-estab- 
lishes the  cycle. 


FIG.    47. — EXPANSION    STEAM    TRAP. 

Other  taps  act  by  differential  expansion  as  that 
of  Holden  and  Brooke  (Figs.  46-47),  shown  in  more 
detail  in  Figs.  48-49. 

When  the  central  pipe  A  fills  with  water  and 
becomes  cooler  it  shortens  and  pulls  the  two  abut- 
ments DK  against  the  round-ended  strut  pieces  R  Rt 
thus  opening  the  valve  E  and  compressing  the  spring 

130 


DRAINAGE 


FIG.    48.— VALVE  OF    STEAM    TRAP. 


POSITION  FOR  TEST 
DISCHARGE 


FIG.   49.— SECTION  OF  EXPANSION  STEAM  TRAP. 


STEAM    PIPES 

at  Z),  which  acts  promptly  to  close  the  valve  again 
as  soon  as  the  central  pipe  expands  on  becoming 
again  full  of  steam  as  the  water  is  expelled. 
Steam  enters  at  C  and  discharge  takes  place  at  the 
opposite  end.  The  trap  may  be  made  to  blow  at 
any  time  by  depressing  the  handle  T.  It  is  adjusted 
by  the  nut  M. 

Steam  traps  are  necessary  on  drain  pipes  from 
the  boiler  stop-valve  where  this  is  so  placed  as  to 
allow  of  an  accumulation  of  water  above  it.  A 
trapped  drain  must  always  be  placed  at  the  low 
point  of  the  steam-pipe  system  which  is  preferably 
to  be  also  the  steam  or  water  separator. 

As  traps  discharge  into  the  atmosphere  the  escape 
from  a  pipe  under  pressure  is  always  hotter  than 
steam  at  atmospheric  pressure,  and  much  steam 
also  rises  from  a  trap  discharge  in  consequence  of 
the  flashing  into  steam  of  a  part  of  the  water.  The 
discharge  of  a  trap  may  go  to  the  pump  well,  being 
pure  hot  water. 


132 


CHAPTER    XIII 
Junction   Pieces   and   Flanges 

JUNCTION  pieces,  such  as  tees,  Y- junctions, 
crosses,  pockets  and  bends,  are  often  made 
of  cast  iron  for  even  high  pressures,  though  many 
engineers  do  not  approve  of  this  practice,  and  this 
subject  is  elsewhere  referred  to. 

Whatever  the  material,  it  is  essential  that  junc- 
tion pieces  should  be  proportioned  on  well  defined 
rules.  Thus  every  branch  from  a  given  size  of  T 
must  set  the  same  distance  from  the  face  of  the 
branch  flange  to  the  centre  line  of  the  T,  no  matter 
what  diameter  the  branch  may  be.  Similarly  this 
dimension  of  the  T  must  be  the  radius  of  the  quarter- 
bends  of  the  size  of  the  T. 

Only  by  attention  to  such  standard  dimensions 
can  a  system  of  pipes  be  conveniently  designed. 

Thus  a  four-way  cross  piece  is  simply  the  same 
length  as  a  T  on  each  of  its  pair  of  faces,  and  con- 
sequently the  branch  of  a  T  is  half  the  length  of  the 
T,  while  the  elbow  is  like  two  adjacent  flanges  of  a 
cross-piece  joined  by  a  curve,  and  the  height  of  a 
Y-piece  is  the  same  as  the  length  over  a  +,  and  the 
spread  of  the  two  arms  of  the  Y  is  equal  to  the  height. 

133 


STEAM    PIPES 


In  the  Figures  i  to  7  the  dimension  A  is  the  same 
for  all  junctions  of  the  same  size,  and  the  four  pieces 
are  all  dimensioned  A  or  A  +  2,  and  these  dimen- 
sions as  made  by  the  Babcock  Co.  are  given  in  the 
annexed  table. 

TABLE  OF  TEES,  CROSSES,  ELBOWS,  Y-PIECES,  ETC. 


in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

in. 

Dia. 

2 

2i 

3 

3i 

4 

5 

6 

7 

8 

9 

10 

II 

12 

14 

A= 

IO 

12 

12 

14 

14 

16 

18 

20 

21 

24 

26 

28   28 

30 

The  weight  of  steel  pipe  with  wrought  steel 
flanges  as  made  by  the  Babcock  Co.  is  given  in  the 
Table  X!A.,  p.  37,  and  the  weights  of  cast  equal 
tees,  elbows,  Y-pieces  and  crosses,  are  as  per  Table 
XXIII. 

To  preserve  homogeneity  of  design  wrought  junc- 
tion pieces  or  cast-steel  pieces  should  have  the  same 
linear  dimensions  as  cast  pieces. 

Under  the  head  of  materials  will  be  found  other 
standard  dimensions  of  junction  pieces,  both  cast 
and  wrought,  with  further  remarks  on  the  subject, 
especially  as  regards  elbows.  An  elbow  strictly 

A 

must  be  of  the  same  size  —  as  the  set  of  a  tee   in 

2 

order  that  a  pipe  system  may  be  homogeneous  in 
design,  but  this  does  not  apply  to  true  bends  which 
may  be  of  very  large  radius  ;  no  bend  should  have 
a  radius  less  than  three  diameters,  five  diameters 
may  be  considered  a  minimum  for  really  first-class 
practice. 

134 


JUNCTION    PIECES   AND    FLANG-ES 

Junction  pieces  may  be,  as  stated,  either  of  cast 
iron  for  limited  pressures,  cast  steel  or  mild  steel  for 


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high  pressures.     The  mild  steel  and  the  cast  steel 
tee  junction,  as  arranged  by  Yates  &  Thorn,  are 

i35 


JUNCTION    PIECES    AND    FLANGES 

shown  in  Figs.  50  and  51.  The  flanges  are  here 
shown  with  the  shallow  spigot  and  socket  elsewhere 
described.  It  is  obvious  that  the  recess  offers  a 
great  safeguard  against  rupture  of  the  packing,  but 
it  is  often  a  great  hindrance  to  the  removal  of  a  pipe. 
It  has  been  suggested  that  the  depth  of  the  recess 
should  be  less  than  the  thickness  of  the  joint  ring, 
so  that  this  can  be  sawn  through  if  necessary  to  part 
the  pipe.  Purely  metallic  joints  of  course  do  not 
adhere. 

FLANGES. 

Since  flanged  joints  are  the  most  usual,  it  is  of 
importance  that  their  dimensions  should  be  stand- 
ardized. The  lack  of  a  standard  has  proved  an 
immense  inconvenience.  There  are  five  points  to 
be  standardized. 

(a)  Flange  diameter. 

(&)  Bolt  circle  diameter. 

(c)  Number  of  bolts. 

(d)  Size  of  bolts. 

(e)  Thickness  of  flange. 
(/)  Angle  of  bolt  holes. 

The  dimension  (e)  is  only  for  convenience  in 
ordering  bolts. 

It  would  be  impossible  in  the  space  of  this  book 
to  publish  all  the  principal  flange  tables. 

I  have  selected  a  very  few  only,  viz.  : — 

Those  of  the  Babcock  &  Wilcox  Co.,  because  so 
largely  employed. 

The  standards  of  the  British  Electric  Traction  Co., 

i37 


STEAM    PIPES 


kindly  supplied  me  by  Mr.  A.  J.  Lawson,  of  that 
Company,  and  practically  the  standard  of  the  Brush 
Company  (Tables  XXIV.,  XXV.  ;  Figs.  52,  53) 

The  American  Standard  of  1902. 

The  German  standard  is  omitted  because  it  em- 
ploys numbers  of  bolts  not  divisible  by  four,  and 
therefore  awkward  and  academic. 

James  Russell  &  Sons'  standard. 

The  cast-iron  standard  of  the  Crane  Co.  of  Chicago. 

TABLE    XXIV. 

B.E.T.  Co.  STANDARD  STEAM,  FEED  DELIVERY  AND  SUCTION 
PIPE  FLANGES. 


Dimensions  of  Pipes  and  Flanges. 

Bolts. 

A 

B 

C 

D 

E 

F 

G 

H 

No. 

Dia. 

Length 

in. 

i 

in. 
2J 

in. 

3i 

in. 

1 

in. 

i 

in. 

1 

in. 
I& 

in. 
Ift 

4 

in. 

i 

in. 

if 

1 

2j 

4i 

I 

J 

J 

Ii 

ii 

4 

i 

if 

i 

3t 

4i 

1 

i 

I 

I| 

2 

4 

i 

if 

ii 

3i 

4i 

f 

1 

I 

2i 

2| 

4 

i 

i| 

ii 

4 

5t 

1 

i 

ii 

2i 

2| 

4 

S 

2i 

ii 

4i 

6 

1 

i 

ii 

2| 

2i 

4 

i 

2i 

2 

5 

6J 

1 

1 

ii 

3i 

3i 

8 

i 

2i 

2J 

5 

6J 

1 

1 

ii 

31 

3  1 

8 

* 

2i 

2i 

5i 

7 

1 

i 

il 

3i. 

4 

8 

i 

2i 

21 

51 

7i 

i 

i 

i| 

4, 

4i 

8 

1 

2| 

3 

6* 

7i 

1 

i 

i* 

4f 

4i 

8 

i 

z| 

3i 

6f 

71 

1 

f 

ii 

41 

4J 

8 

f 

2i 

3i 

6f 

8 

1 

5 

i| 

4i 

5 

8 

1 

2i 

31 

7 

81 

J 

J 

i| 

5i 

51 

8 

i 

2i 

4 

7i 

9 

1 

I 

if 

5i 

51 

8 

I 

2f 

5 

8| 

10} 

I 

1 

2 

6i 

6| 

8 

i 

2| 

6 

10 

12 

i 

I 

2 

7i 

7i 

8 

i 

2i 

7 

ii 

13 

i 

1 

2 

8i 

8J 

12 

f 

2| 

8 

12 

14 

7 
8 

ii 

2i 

9i 

9i 

12 

! 

3i 

138 


JUNCTION    PIECES    AND    FLANGES 


TABLE   XXV. 

B.E.T.  Co.  STANDARD  EXHAUST  AND  CIRCULATING  PIPE 
FLANGES. 


Dimensions  of  Pipes  and  Flanges. 

Bolts. 

A 

B 

c 

D 

E 

F 

G 

No. 

Dia. 

Length 

in. 

ft.     in. 

ft.     in. 

in. 

in. 

in. 

in. 

in. 

in. 

2j 

o    54 

o    7 

f 

f 

i 

4 

4 

4 

2 

3 

o    6 

o     7* 

! 

1 

* 

4 

4 

1 

2| 

3i 

o    6J 

o     8 

1 

1 

A 

4 

4 

1 

2f 

4 

o    7i 

o     9 

I 

f 

i 

1 

8 

4 

2i 

44 

o     8 

o     94 

i 

! 

4 

1 

8 

4 

2i 

5 

o     8} 

o  ioj 

i 

i 

4 

f 

8 

1 

2| 

6 

0    IO 

I       O 

i 

f 

j 

1 

8 

1 

2| 

7 

0    I0| 

I     I 

i 

1 

4 

1 

8 

f 

2| 

8 

I      0 

I      2 

! 

1 

ft 

4 

8 

f 

2f 

9 

I    I 

i     3 

1 

I 

* 

f 

12 

4 

3 

10 

I      2j 

i     4i 

I 

I 

f 

i 

12 

f 

3 

ii 

i     3 

i     5 

i 

I 

f 

i 

12 

I 

3 

12 

i     5 

i     7i 

1 

ii 

1 

1 

12 

1 

3l 

13 

i     6 

i     8J 

I 

ii 

i 

1 

12 

1 

3l 

14 

i     7 

i     94 

i 

ii 

i 

i 

12 

i 

3i 

16 

i     9J 

2      O 

I 

if 

i 

I 

12 

i 

3! 

FIG.    52. — FLANGES    (B.E.T.  CO.    STANDARD). 
139 


STEAM    PIPES 

As  regards  the  number  of  bolts  this  should  always 
be  divisible  by  four,  and  should  never  be  less  than 
eight,  if  eight  bolts  can  be  got  in.  The  size  of  a 
bolt  should  not  be  less  than  f-inch,  and  the  holes 
should  be  ^--inch  larger  than  the  bolts.  This  rule 
gives  excessive  bolt  strength  in  some  sizes  where 
the  jump  is  made  to  an  additional  four  bolts,  but 
the  J-inch  bolt  is  not  a  satisfactory  thing  in  practical 
engineering  unless  of  manganese  steel. 


FIG.    53. 

The  advantage  of  the  multiple  of  four  is  that  a 
piece  can  always  be  turned  through  an  angle  of 
go0  and  bolts  will  still  come  right.  The  arrange- 
ment of  bolt  holes  should  always  be  so  that  no  hole 
comes  on  a  centre  line. 

The  pitch  of  bolts  should  not  exceed  4^  inches, 
according  to  Mr.  Atkinson.  As  soon  as  with  a 
given  number  of  bolts  the  pitch  becomes  4^  inches, 
the  next  size  of  pipe  should  have  an  additional  four 
bolts.  Thus  with  his  7-inch  pipe  the  bolt  circle  is 
n|-  inches,  and  the  pitch  of  8  bolts  is  4-51.  His 
8 -inch  pipe,  therefore,  has  12  bolts. 

140 


JUNCTION    PIECES    AND    FLANGES 


TABLE  XXVI. 

BABCOCK  &  WILCOX  STANDARD  FLANGES. 


Bore. 

High  Pressure  Steam. 

Exhaust. 

Feed. 

Diam. 
of 

Flanges 

No. 
of 
Bolts. 

Diam. 
of  Pitch 
Circle. 

Size 
of 
Bolts. 

Diam. 
of 

Flanges 

No. 
of 
Bolts. 

Diam. 
of  Pitch 
Circle. 

Size  !  Diam. 
of          of 
Bolts.  !  Flanges 

No. 
of 
Bolts. 

Diam. 
of  Pitch 
Circle. 

Size 
of 
Bolts. 

ins. 

ins. 

ins. 

in. 

ins. 

ins. 

in.          ins. 

ins. 

in. 

I 

3* 

4 

2* 

| 



— 



-      3* 

4 

2* 

I 

I 

4* 

4 

3* 

* 



— 



41 

4 

3* 

* 

I* 

4* 

4 

3* 

1 



— 



-      4*. 

4 

& 

} 

Ii 

5 

4 

4        * 



— 



—      5 

4 

4 

* 

2 

7 

6 

5* 

5 

£ 



— 



—      6 

4 

4* 

1 

2* 

7l 

6 

6 

0 
f 



— 



—      7 

4 

Si 

1 

3 

8| 

6 

6| 

1 

'  

— 



8* 

4 

6* 

1 

3* 

9 

6 

7* 

1 



— 



— 

— 



4 

10 

8 

8* 

*        9 

4 

7*      * 

9i 

6 

71 

1 

5 

ii 

8 

9 

I          10* 

6 

8*      * 

— 

— 

— 



6 

12 

8  I  10 

1 

IX* 

6 

9*      1       - 

— 

— 



7       H 

12 

ii| 

1 

12*          6 

io*      * 

— 

— 

— 



8    |   14 

12 

12* 

1 

13* 

8 

12 

*       - 

— 

— 



9 

15 

12 

13* 

1 

14* 

8 

13            1 

— 

— 

— 



10 

17 

12 

14* 

1 

15* 

8 

14           1 

— 

— 

— 



ii 

1  8* 

12 

16 

1 

i6f 

12 

15        1 

— 

— 

— 



12 

19* 

12 

17* 

1 

17* 

12 

16        | 

— 

— 

—  • 



13 



— 

-      19* 

12 

i7l      1 

— 

— 

— 



14 

— 



— 

20* 

12 

18*      1 

— 

— 

— 



15 

— 



— 

— 

21* 

12 

19*      I 

— 

— 

— 



16 

— 



— 

— 

22* 

12 

20*        | 

— 

— 

— 



17 

— 

— 

— 

— 

23i 

16 

21*        1 

— 

— 

— 



18 

— 



— 

— 

24i 

16 

22|         | 

— 

— 

— 



20 

— 



— 

— 

26i 

16 

24* 

1 

— 

— 

— 



22 



— 

— 

— 

28| 

20 

27 

1 

— 

— 

— 



24 

— 



— 

— 

30* 

20 

29 

* 

— 

— 

— 



The  author  is  inclined  rather  to  limit  the  pitch 
to  4  inches,  thus  giving  12  bolts  to  the  7-inch  pipe 
as  practised  by  the  Crane  Co. 

Ordinary  commercial  bolts  tested  by  Professor 
Goodman  have  shown  a  tensile  strength  of  29  to 
35  tons  per  square  inch,  the  smaller  bolts  coming 

141 


STEAM    PIPES 


out  best,  but  bolts  in  practice  are  exposed  to  a  tor- 
sional  stress,  and  the  smaller  bolts  are  apt  to  have 
the  biggest  stresses  put  on  them,  and  it  is  wise  to 
keep  to  I  as  a  minimum  size  where  possible. 

TABLE    XXVII. 

DIMENSIONS  OF  CAST-IRON  FLANGED  FITTINGS  AND  CONNEC- 
TIONS, AS  USED  BY  CRANE  COMPANY,  CHICAGO. 


Inside 
Diameter  of 
Pipe. 

Diameter  of 
Flange. 

Diameter 
of  Bolt 
Circle. 

Number  of 
Bolts. 

Set  of  T- 
Branch  or 
Quarter  Bend, 
etc. 

Length  of  a 
T. 

ins. 

ins. 

ins. 

ins. 

ins. 

2 

6 

41 

4 

4i 

9 

2i 

7 

Si 

4 

5 

IO 

3 

7i 

6 

4 

5i 

ii 

3i 

8* 

6} 

4 

6 

12 

4 

9 

7i 

8 

6J 

13 

4i 

9i 

71 

8 

7 

14 

5 

IO 

8* 

8 

7i 

15 

6 

II 

9t 

8 

8 

16 

7 

I2| 

II 

12 

8J 

17 

8 

13  J 

12 

12 

9i 

19 

9 

15 

13 

12 

io| 

2lJ 

IO 

16 

I4J 

12 

nt 

23 

12 

19 

17 

16 

I2| 

25i 

14 

21 

i8J 

16 

13^ 

26J 

16 

23i 

2lJ 

20 

i5t 

3°i 

18 

25 

22j 

20 

i6J 

33 

20 

27i 

24! 

2O 

18 

36 

22 

294 

27J 

24 

20 

40 

24 

31* 

2QJ 

24 

22 

44 

For  very  special  work  bolts  of  manganese  steel 
may  be  procured,  which  are  greatly  superior  to 
ordinary  bolts. 

Mr.  E.  R.  Briggs  proposes  as  a  suitable  stress  for 
bolts,  /  =  5,000  d,  where  d  is  the  nominal  bolt  dia- 

142 


JUNCTION    PIECES    AND    FLANGES 

meter.     This  gives  the  following  stresses  per  square 
inch  to  be  allowed  in  any  bolt : — 

Bolt.  / 

J-in.  =          2,500  pounds 
t  „•  3,125       „ 

I  „  3,750       „ 

J  „  4,375       „ 

i     „  =         5,000       „ 


,,  and  over  — 


5,625 


He  would  never  allow  /  to  exceed  6,000  pounds. 
The  rule  allows  for  the  weakness  and  liability  to 
overstress  of  small  bolts. 

TABLE    XXVIII. 

TANDARD   FLANGES  ADOPTED    BY    MESSRS-  JAMES  RUSSELL 
AND  SONS,  CROWN  TUBE  WORKS,  WEDNESBURY 


Inside 
Diameter  of 
Pipe. 

Outside 
Diameter  of 
Flange. 

Inside 
Diameter  of 
Pipe. 

Outside 
Diameter  ot 
Flange. 

inches. 

inches. 

inches. 

inches. 

4 

3* 

5 

IO 

i 

3* 

54 

104 

i 

4i 

6 

"4 

it 

5 

64 

I2J 

14 

54 

7 

13 

if 

54 

74 

i34 

2 

6 

8 

14 

2J 

61 

84 

i44 

2i 

7 

9 

15 

2| 

74 

94 

i54 

3 

8 

10 

164 

3i 

84 

104 

17 

31 

84 

II 

i74 

3l 

9 

"J 

18 

4 

9 

12 

184 

44 

94 

143 


STEAM    PIPES 


TABLE    XXIX. 

STANDARD  FLANGES  ADOPTED  IN  AMERICA,  JANUARY,   i,  1902, 
FOR  PRESSURES  101  LB.  TO  250  LB. 


Diameter 
of 
Pipe. 

Diameter 
of 
Flange. 

Thickness 
of 
Flange. 

Diameter 
of 
Bolt  Circle. 

Number 
of 
Bolts. 

Size 
of 
Bolts. 

ins. 

ins. 

ins. 

ins. 

ins. 

2 

6J 

1 

5 

4 

1 

2* 

7i 

I 

51 

4 

i 

3 

8i 

ii 

6f 

8 

t 

3i 

9 

i* 

71 

8 

i 

4 

10 

il 

7J 

8 

! 

4i 

ioi 

i* 

8J 

8 

1 

5 

ii 

if 

9i 

8 

i 

6 

12} 

i* 

I0| 

12 

1 

7 

14 

i* 

"I 

12 

i 

8 

15 

i| 

13 

12 

i 

9 

16 

i| 

14                     12 

i 

10 

i7i 

ij 

i6i 

16 

i 

12 

20 

2 

171 

16 

i 

14 

22J 

2* 

2O 

20 

i 

15 

23i 

2* 

21 

20 

i 

16 

25 

21 

22J 

2O 

i 

18 

27 

2| 

24* 

24 

i 

20 

29i 

2i 

26J 

24 

ii 

22 

3ii 

2f 

28| 

28 

ii 

24 

34 

2j 

3il 

28 

ii 

144 


CHAPTER    XIV 

Separators,    Exhaust    Heads    and    Atmo- 
spheric   Valves 

A  WATER  separator  for  removing  the  surplus 
water  from  saturated  steam  acts  always  on 
the  principle  of  the  first  law  of  motion,  taking  into 
effect  the  tendency  of  an  inert  body  such  as  water 
to  move  in  a  straight  line.  All  separators,  there- 
fore, act  by  causing  the  flow  of  steam  to  be  suddenly 
reversed  in  direction.  The  steam  follows  the  new 
path  and  the  water  continues,  and  is  caught  in  a 
suitable  receptacle  and  trapped  off.  There  are 
legions  of  separators  in  the  market,  but  all  work  on 
the  same  principle.  Two  or  three  forms  only  are 
therefore  illustrated,  that  of  Holden  &  Brooke 
(Fig.  54),  and  those  of  Yates  &  Thorn  (Figs.  55,  56). 

EXHAUST  HEADS, 

for  preventing  the  escape  of  oil  and  water  at 
atmospheric  discharges,  act  on  the  same  prin- 
ciple, affording  a  large  internal  area  for  the 
steam,  and  a  quiet  part  for  the  collection  of  oil 
gathered  in  the  cones  and  on  the  outer  cylinder. 


STEAM    PIPES 

Fig.  57  is  the  exhaust  head  of  Holden  &  Brooke, 
who  make  them  so  that  a  5-inch  head  will  deal  with 
1,000  pounds  of  exhaust  steam  per  hour,  a  lo-inch 


DRAIN 

FIG.    54. WHIRLING    SEPARATOR    (HOLDEN    &    BROOKE). 

with  3,060  pounds,  a  i6-inch  with  9,000  pounds,  and 
a  24-inch  with  25,000  pounds,  and  pro  rata. 

146 


SEPARATORS 


ATMOSPHERIC  VALVES. 

Where  an  alternate  exhaust  is  desired  to  a  con- 
denser, or  to  atmosphere,  a  valve  is  fitted  in  the 


FIG.    55.  FIG.    56. 

REVERSE    FLOW    STEAM    AND    WATER    SEPARATORS    (YATES    &    THOM). 

atmospheric  exhaust  proper,   which  will  automati- 
cally open  and  close  when  condensation  ceases  or 

i47 


STEAM    PIPES 

resumes.  These  valves  ought  to  have  a  shallow 
water  seal  above  them  so  as  to  obviate  any  air  leak- 
age. An  oil  dashpot  ought  to  be  fitted  outside  the 
body  to  prevent  hammering  of  the  valve,  which  will 
occur  if  no  dashpot  is  present  or  only  an  air  dash- 
pot  be  employed. 


FIG.    57. EXHAUST    HEAD    (HOLDEN    &    BROOKE). 

A  glass  water-gauge  should  show  the  depth  of 
water-seal,  and  a  drain  pipe  should  prevent  its  be- 
coming too  deep.  A  supply  pipe  should  also  keep 
up  a  supply  of  water  or  the  seal  may  leak  away  and 
air  may  leak  in.  The  atmospheric  valve  is  so 
frequent  a  cause  of  bad  vacuum  that  it  deserves 
more  attention  than  it  usually  obtains.  One  of 
these  valves  by  Templer  &  Ranoe  is  shown  in  Fig.  58. 
It  can  be  placed  upside  down  equally  well.  There 
is  an  outside  oil  dashpot.  An  automatic  exhaust 

148 


SEPARATORS 


FIG.    58. — ATMOSPHERIC   EXHAUST   VALVE. 


149 


STEAM    PIPES 

valve  by  Thos.  Walker,  of  Tewkesbury,  is  shown 
in  Fig.  59.  This  is  shown  with  the  customary  air 
dashpot,  but  oil  can  be  substituted.  In  the  author's 


opinion  the  air  dashpot  is  what  is  responsible  for 
the  clatter  of  atmospheric  valves  when  opening  and 
closing  under  the  pulsation  of  the  exhaust.  He  would 
fill  the  dashpot  with  oil  on  both  sides  of  the  piston, 

150 


SEPARATORS 

and  in  place  of  the  snifting  valves  would  connect 
the  top  and  bottom  of  the  cylinder  by  a  small  pipe 
with  a  valve.  By  regulating  this  valve  the  proper 
action  of  the  automatic  exhaust  valve  would  be 
better  secured.  An  air  dashpot  can  be  converted 
into  an  oil  dashpot  by  means  of  a  small  cock  and  a 
bit  of  pipe  joining  the  opposite  ends  of  the  cylinder. 


CHAPTER    XV 
Superheated  Steam 

THE  fact  is  well  recognized  that  moisture  in 
steam  is  one  of  the  great  causes  of  friction 
and  resistance  to  flow.  The  water  is  inert.  When 
it  strikes  the  pipe  surface  it  is  stopped  in  its  progress, 
and  it  continually  puts  a  drag  on  the  steam.  Steam 
dried  and  superheated  undoubtedly  travels  faster, 
but  experiment  is  wanting  to  say  to  what  extent. 
It  is  possible  that  more  superheated  steam  will  pass 
through  a  given  pipe  in  a  given  time  with  a  given 
loss  of  pressure  than  is  the  case  with  saturated 
steam. 

The  volume  of  superheated  steam  varies  with  its 
absolute  temperature  very  approximately.  Thus 
steam  at  360°  F.  has  an  absolute  temperature  of 
360  +  459,  or  819°.  Superheated  100°  F.,  its  volume 
is  now  increased  in  the  ratio  (819  +  100)  :  819,  or 
about  12  per  cent.  Superheated  200°  F.,  the  volu- 
metric increase  is  nearly  24  per  cent.  With  modern 
pressures  the  temperature  of  superheat  will  rarely 
exceed  200°  above  saturation  temperature. 

Mr.  Cruse  makes  the  cross-section  of  the  pipes  of 
his  superheater  from  25  per  cent,  for  high  pressures 
to  50  per  cent,  for  low  pressures  in  excess  of  the 

152 


SUPERHEATED    STEAM 

boiler  steam  pipe.  With  this  provision  the  loss  of 
pressure  in  traversing  the  long  pipe  superheater  is 
always  under  three  pounds,  and  more  usually  only 
one  pound  to  two  pounds.  The  superior  mobility  of 
.superheated  steam  is  probably  such  that  the  size 
of  the  steam  pipe  need  not  be  increased  for  a  given 
weight  of  steam.  Where  the  same  power  is  to  be 
developed,  the  diminution  of  the  weight  of  steam 
required  will  not  differ  far  from  the  inverse  ratio  of 
the  increase  in  volume  due  to  superheat.  On  the 
whole,  therefore,  for  a  given  power  the  steam  pipes 
may  be  less  in  size  than  usually  provided. 

PIPE  COVERINGS. 

Every  manufacturer  of  pipe  coverings  will  pro- 
duce figures  to  show  that  his  special  material  is  the 
best. 

It  is  certain  that  almost  anything  sold  will  pay 
for  itself  in  steam  saved. 

The  best  of  all  material  is  loose  wool.  Loose 
lamp-black,  down  and  hair-felt  come  next,  and 
generally  it  may  be  said  that  the  best  heat  insu- 
lators are  those  which  imprison  the  most  air  in  a 
finely  divided  condition.  But  all  organic  sub- 
stances are  unsuitable  for  the  modern  conditions 
with  superheated  steam,  and  some  form  of  magnesia 
covering  or  other  similar  preparation  is  probably 
best. 

Coverings  are  sometimes  put  on  in  a  soft  plastic 
condition  and  hardened  in  place  by  the  heat  of  the 


STEAM    PIPES 

pipe.  Others  are  built  up  into  sections  and  fitted 
to  the  pipes  and  held  by  wire-binding,  or  clips  of 
hoop-iron,  or  by  hooks  and  eyes.  The  neatest  cover- 
ing has  an  outer  case  of  Russia  iron.  In  all  cases 
the  flanges  ought  to  be  covered.  No  covering 
should  be  less  than  one  inch  in  thickness.  .This  may 
be  exceeded  if  the  value  of  the  heat  saved  renders  it 
economical,  and  often  it  will  pay  to  put  two  inches 
of  covering  upon  a  pipe. 

Numerous  tests  have  been  made  from  time  to 
time  by  various  experimenters  on  different  sub- 
stances, and  particulars  of  these  tests  may  be  found 
in  the  Proceedings  of  the  American  Society  of  Mechani- 
cal Engineers.  Tables  and  data  may  be  found  in 
Kempe's  Year  Book  and  in  Steam y  and  in  various 
other  pocket-books  and  in  the  catalogues  of  makers 
of  coverings.  From  one  of  these  it  appears  that  the 
composition  prevented  five-sixths  of  the  loss  with 
bare  pipes. 

A  thickness  of  one  inch  of  hair-felt  also  reduced 
condensation  to  one-sixth,  two  inches  of  felt  reduced 
it  to  one-eleventh,  while  the  abnormal  thickness  of 
six  inches  reduced  it  to  one-twenty-fourth. 

Small  pipes  lose  relatively  more  than  large  pipes 
because  the  area  of  an  equal  thickness  of  covering 
is  greater.  It  is  also  more  costly  to  cover  small 
pipes  because  the  same  thickness  or  more  is  neces- 
sary, and  the  area  of  a  small  pipe  and  its  steam- 
carrying  capacity  is  less  per  unit  of  superficial  area. 
As  a  general  rule  it  will  be  good  practice  to  employ 
coverings  ij  inch  thick,  unless  experiment  can 

i54 


SUPERHEATED    STEAM 

be  made  to  determine  the  economy  of  a  different 
thickness  by  equating  the  interest  charge  of  the 
covering  and  the  fuel  value  of  the  heat  loss,  remem- 
bering that  in  a  hardly-pressed  plant  an  additional 
outlay  on  pipe  coverings  might  render  it  possible 
to  avoid  adding  extra  boilers. 

It  is  possible  of  course  to  cover  a  pipe  first  with 
magnesia,  and  upon  this  with  hair-felt,  which  would 
be  protected  from  the  most  severe  heat  by  the  inner 
mineral  layer. 

Coverings  which  are  liable  to  loosen  or  disin- 
tegrate under  vibration  should  be  avoided. 

Slag-wool  is  apt  to  do  this,  and  it  is  heavy  and 
is  liable  to  cause  trouble  if  it  gets  into  machinery 
bearings.  Lightness  is  a  favourable  quality  in  a 
covering  because  it  indicates  considerable  air  space, 
a  feature  which  is  sought  in  fossil  meal  in  the  shape 
of  the  minute  cavities  of  the  diatoms  ;  in  certain 
asbestos,  corrugated  millboards,  and  in  wool-felt, 
both  in  the  fibre  itself  and  the  frictional  effect  by 
which  the  myriads  of  fibres  hold  the  air  from  cir- 
culating. The  non-circulation  of  air  inside  the 
mass  of  the  covering  is  one  of  the  more  valuable 
features  of  the  best  compositions. 

The  very  common  practice  of  leaving  pipe  flanges 
and  bolt  heads  and  nuts  bare  of  protection  is  neces- 
sary with  the  plastic  compounds  which  are  stopped 
off  short  of  the  flanges,  but  this  is  no  excuse  for 
neglecting  to  provide  loose  covers  over  the  flanges. 

A  few  tables  and  deductions  abstracted  from  a 
report  by  Mr.  Atkinson,  of  Boston,  relative  to  the 

i55 


STEAM    PIPES 

tests  of  Mr.  C.  E.  L.  Norton,  on  pipe  coverings,  will 
be  useful.  They  have  been  translated  on  the  basis 
of  £i  =  $5,  and  they  are  probably  as  accurate  as 
any  tests  made,  and  will  afford  a  useful  guide  to  the 
engineer  who  wishes  to  have  his  pipes  dealt  with  in 
the  manner  that  the  importance  of  the  question 
demands. 

The  tests  were  made  in  1898  by  Mr.  Norton, 
on  pipe  coverings  of  various  types.  He  employed 
an  electrically-heated  apparatus  with  coils  of  wire 
in  a  bath  of  oil,  and  by  maintaining  the  oil  at  a  fixed 
temperature  he  was  able  to  measure  the  heat  gener- 
ated, and  therefore  lost,  by  the  measure  of  the 
current  consumed.  Particulars  of  the  test  need  not 
be  detailed ;  they  may  be  found  in  Circular  Note  of 
the  Mutual  Boiler  Insurance  Co.,  of  31,  Milk  Street, 
Boston,  U.S.A.,  1898. 

A  few  of  the  tabulated  results  are  here  abstracted, 
and  it  may  be  added  that  Mr.  Edward  Atkinson, 
selected  A,  D,  G,  E  as  safe  in  respect  of  safety  from 
fire  and  efficiency  in  results. 

Articles  containing  lime  sulphate  are  not  advised 
because  of  the  danger  of  corrosion  of  the  covered 
pipe,  and  many  so-called  magnesia  coverings  con- 
tain rather  lime  sulphate  than  magnesia.  Magnesia 
of  course  is  good  if  it  can  be  obtained  really  pure 
and  unadulterated.  Mr.  Norton  also  recommended 
plastic  coverings  as  better  than  sectional  for  certain 
conditions,  and  especially  where  vibration  is  likely 
to  occur.  Sectional  coverings  are  looked  on  usually 
as  better  than  plastic.  Yet  at  least  20  per  cent,  of 

156 


SUPERHEATED    STEAM 

plastic  must  always  be  employed  for  the  irregular 
surfaces. 

The  tables  which  follow  are  at  least  sufficient 
as  a  general  guide,  and  prove  the  undisputed  benefit 
of  good  coverings. 

Specimen  A,  Nonpareil  cork  standard,  consists  of 
granulated  cork,  pressed  in  a  mould  at  high  tem- 
perature and  then  submitted  to  a  fire-proofing 
process. 

Specimen  B,  Nonpareil  cork  octagonal,  is  similar 
in  composition,  but  is  made  up  of  several  strips  of 
cork,  instead  of  two  semi-cylindrical  sections. 

Specimen  C,  Manville  high-pressure  sectional 
cover,  is  composed  of  an  inner  jacket  of  earthy 
material  and  an  outer  jacket  of  wool- felt,  the  whole 
being  one  and  one-quarter  inches  thick. 

Specimen  D,  magnesia,  is  a  moulded,  sectional 
cover,  composed  of  about  90  per  cent,  carbonate 
of  magnesia. 

Specimen  E  is  essentially  an  air  cell  cover,  being 
composed  of  sheets  of  asbestos  paper  which  has  been 
indented  before  being  laid  up,  the  indentations 
serving  to  keep  the  thin  sheets  of  paper  from  coming 
into  close  contact  with  one  another,  thereby  causing  a 
considerable  amount  of  air  to  be  held  throughout 
the  body  of  the  cover. 

Specimen  F  is  composed  of  a  wool-felt  with  a 
lining  of  asbestos  paper. 

Specimen  G  is  a  cover  made  up  of  thin  sheets  of 
asbestos  paper,  fluted  or  corrugated,  and  stuck 
together  with  silicate  of  soda. 

157 


9 

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lit 

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o  o  v 

in  t^  (NI  t^s  oo  oo   o   o   o   o   H   H   ~t~  ^o   c 

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Specimen. 

<jpQcjQWfeOM'-<  ^—  >W  H-J  O  P* 

158 


SUPERHEATED    STEAM 

Specimen  H  is  a  plastic  covering  made  of  infusorial 
earth. 

Specimen  I  is  similar  to  Specimen  F. 

Specimen  J  is  a  plastic  cover  called  magnesia- 
asbestos.  It  contains  only  a  slight  amount  of  car- 
bonate of  magnesia. 

Specimen  K  is  a  moulded  cover,  containing  about 
45  per  cent,  of  carbonate  of  magnesia  and  a  con- 
siderable percentage  of  carbonate  of  calcium. 

Specimen  L  is  composed  mainly  of  sulphate  of 
calcium  and  some  20  per  cent,  of  MgCO3  and  has 
upon  its  outer  surface  a  thick  sheet  of  felt  board. 

Specimen  O  is  similar  to  Specimen  G,  except  that 
it  has  larger  cells  and  contains  much  more  silicate 
of  soda.  It  is  very  hard  and  strong. 

Specimen  P  is  a  sectional,  moulded  cover,  com- 
posed mainly  of  sulphate  of  calcium.  It  has  an 
outer  layer  of  felt  board. 

Of  Specimens  C,  J,  L,  and  P,  the  principal  in- 
gredient is  stated  to  be  sulphate  of  lime  and  not 
carbonate  of  magnesia.  Prospective  purchasers  ol 
pipe  covers  should  not  be  misled  by  names.  Since 
the  appearance  of  Professor  Ordway's  reports  it 
has  been  recognized  that  carbonate  of  magnesia 
is  of  great  value  as  a  non-conductor  of  heat,  hence 
the  name  "  magnesia  "  has  been  applied  to  a  great 
many  covers.  It  is  to  be  observed  that  there  is  no 
virtue  in  a  name.  Asbestos  is  merely  an  incom- 
bustible material  in  which  air  may  be  entrapped, 
but  when  not  porous  is  a  good  conductor  of  heat. 
Magnesia  is  a  most  effective  non-conductor.  This 

159 


STEAM    PIPES 


name  has  been  applied  to  many  compounds  of  which 
the  greater  part  consists  of  carbonate  of  lime  or  of 
plaster  of  Paris,  materials  which  are  not  good  as 
heat  retarders.  The  percentage  of  magnesia  car- 
bonate and  plaster  of  Paris  in  several  moulded, 
sectional  covers  is  given  in  Table  B. 

The  Cork,  Magnesia,  Air  Cell,  and  Imperial  covers 
cause  no  corrosion. 

TABLE   B. 


Percentage  Composition. 

Specimen. 

MgC03 

CaS04 

Carbonate  of  Magnesia. 

Sulphate  of  Calcium. 

D 

80  to  90 

3 

C 

less  than  5 

65  to  75 

L 

20  to  25 

50  to  60 

P 

less  than  5 

75 

J 

10  to  15 

none 

The  conditions  of  testing  were  reasonably  near 
the  conditions  of  actual  practice.  The  room  tem- 
perature was  kept  at  72°  F.  and  the  openings  into 
the  room  were  carefully  closed.  It  was  found  early 
in  the  series  that  variation  in  the  amount  of  moisture 
present  in  the  air  altered  the  amount  of  heat  lost 
from  the  covers,  but  no  attempt  was  made  to 
correct  this.  The  error  introduced  is  not  greater 
than  i  per  cent. 

It  was  found  that  the  heat  loss  per  square  inch  of 
the  flat  surfaces  at  the  ends  of  the  pipes  was  less  by 
several  per  cent,  than  the  loss  from  the  sharply 

1 60 


SUPERHEATED    STEAM 

curved  sides,  and  as  all  pipe  covers  tested  were  used 
to  cover  both  sides  and  ends,  the  figures  given  in  the 
table  show  a  loss,  less  than  would  be  shown  were 
the  pipe  surface  wholly  cylindrical,  and  more  than 
if  it  were  all  flat. 

The  pipes  were  suspended  from  the  ceiling,  as 
described  in  an  early  paragraph,  and  the  air  cir- 
culating about  them  was  due  only  to  their  own  convec- 
tion currents.  The  variation  in  thickness  in  different 
places  on  the  same  specimen  was  considerable,  but 
an  average  of  twenty  measurements  was  taken  and 
results  given  in  the  table  to  the  nearest  one-eighth 
of  an  inch.  Owing  to  these  variations  in  thickness, 
the  results  of  a  measurement  of  the  efficiency  of  any 
one  cover  cannot  be  used  to  predict  the  efficiency 
of  a  second  cover  of  the  same  make  with  an  accuracy 
greater  than  2  per  cent.  Two  specimens  of  each 
make  were  tested,  and,  in  some  cases,  four,  the  mean 
value  being  given  in  the  table. 

Table  C  gives  the  saving,  in  £'s,  due  to  the  use 
of  the  various  covers. 

Table  D  shows  that  at  the  end  of  ten  years  the 
best  of  the  covers  tested  will  have  saved  £9-2  more 
than  the  poorest.  The  difference  between  the  several 
covers  of  the  better  grade  is  exceedingly  small. 

The  money  saving  is  computed  on  the  following 
assumptions  : — Coal  at  sixteen  shillings  a  ton  evap- 
orates ten  pounds  of  water  per  pound  of  coal ;  the 
pipes  are  kept  hot  ten  hours  a  day,  three  hundred 
and  ten  days  a  year.  If  computations  are  made, 
as  is  sometimes  done,  on  an  assumption  that  the 

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162 


SUPERHEATED    STEAM 

pipes  are  hot  twenty- four  hours  a  day,  three  hundred 
and  sixty-five  days  in  a  year,  the  saving  is  nearly 
three  times  that  shown  in  Table  C. 

Generally  speaking,  a  cover  saves  heat  enough 
to  pay  for  itself  in  a  little  less  than  a  year  at  three 
hundred  and  ten  ten-hour  days,  and  in  about  four 
months  at  three  hundred  and  sixty-five  twenty- 
four  hour  days. 

It  is  evident  that  the  decision  as  to  the  choice  of 
cover  must  come  from  other  considerations,  as  well 
as  from  the  conductivity. 

The  question  of  the  ability  of  a  pipe  cover  to  with- 
stand the  action  of  heat  for  a  prolonged  period  with- 
out being  destroyed  or  rendered  less  efficient  is  of 
vital  importance.  The  increasing  use  of  cork  as  an 
insulator  has  led  to  many  questions  as  to  its  ability 
to  reaiain  ff  fire-proof."  Exposed  to  a  temperature 
corresponding  to  three  hundred  and  fifty  pounds  of 
steam  for  three  months,  and  to  a  temperature  corre- 
sponding to  one  hundred  pounds  for  two  years,  no 
change  was  found,  and  any  suspicion  of  its  ability 
to  withstand  continued  heating  is  considered  ground- 
less. 

The  magnesia  covering  is  of  course  unquestion- 
able on  this  ground,  being  almost  indestructible  by 
heating. 

The  Imperial  asbestos  is  also  perfectly  safe  from 
any  fire  risks,  as  is  the  Air-Cell  and  Fire-Board. 

The  Manville  infusorial  earth,  and  also  the  Man- 
ville  magnesia-asbestos  are  liable  to  no  accident 
from  fire,  nor  is  the  Carey  calcite. 

163 


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164 


SUPERHEATED    STEAM 

It  is  not  safe  to  put  upon  a  steam-pipe  wool,  hair- 
felt,  or  woollen  felt  in  any  form.  The  causes  of 
risk  are  two  :  First,  the  wool  may  become  charred 
by  heat  from  the  pipe  and  finally  ignited,  though 
this  can  hardly  happen,  even  on  high-pressure  pipes, 
when  the  thickness  of  fire-proof  material  (asbestos, 
magnesia,  or  whatever  it  may  be)  is  as  great  as  one 
inch.  The  second  and  most  serious  risk  is  from 
the  presence  in  shops  or  mills  of  the  long  tubes  of 
wool,  dry  as  tinder,  often  connecting  one  room  with 
another,  and  ready  to  flash  at  the  slightest  rise  in 
the  already  too  great  temperature.  Canvas  jackets 
on  the  covers  should  be  fire-proof.  The  efficiency 
of  wools  is  high  as  non-conductors,  but  not  higher 
than  any  other  perfectly  safe  covers.  If  the  wool 
is  separated  by  about  one  inch  of  fire-proof  material 
from  the  pipe,  it  is  not  kept  so  hot  and  dry,  and  the 
risks  from  outside  ignition  is  less  ;  but  the  practice 
of  many  engineers  of  wrapping  hair-felt  outside  of  a 
sectional  cover  is  not  advised.  The  saving  due  to 
this  practice  is  indicated  in  Table  E. 

The  following  assumptions  have  been  made  in 
computing  the  Tables  D,  E  and  F.  First,  that  all 
the  covers  cost  £5  per  one  hundred  square  feet, 
applied.  This  is  a  high  figure,  perhaps  too  high,  yet 
it  is  not  far  from  the  list  price  of  several  makers,  and 
any  attempt  to  get  a  definite  price  from  them — 
revealed  a  maze  of  discounts  and  double  discounts 
and  flexible  price-lists  too  intricate  for  an  uninitiated 
mind  to  travel.  In  case  the  saving  due  to  a  cover, 
which  costs  £4  instead  of  £5,  is  desired,  the  simple 

165 


STEAM    PIPES 

addition   to  the  final  saving  of  the  £i   difference 
makes  the  necessary  correction. 

Secondly,  by  the  advice  of  the  makers,  the  assump- 
tion is  made  that  the  cost  is  not  nearly  proportional 
to  the  thickness.  As  the  thicker  coverings  are  not 
now  made  in  great  quantities,  the  actual  cost  of 
their  manufacture  is  uncertain. 

Inspection  of  Table  E  shows  the  saving  due  to 
the  use  of  hair-felt  outside  a  standard  magnesia 
cover. 

In  five  years  one  hundred  square  feet  of  hair-felt 
saves  £1-4°  more  than  its  cost,  and  in  ten  years  it 
saves  £4  above  its  cost. 

The  further  saving  due  to  a  second  inch  outside 
the  first  is  £1-60  in  ten  years.  Of  course  the  well- 
known  tendency  of  hair-felt  to  deteriorate  should 
be  considered. 

In  the  case  of  Nonpareil  cork,  increasing  the  thick- 
ness from  one  to  two  inches  raises  the  cost  from 
about  £5  to  £7  per  one  hundred  square  feet,  and 
increases  the  net  saving  in  five  years  by  £2  and  by 
£6  in  ten  years.  In  other  words,  the  second  inch 
of  material  in  use  about  pays  for  itself  in  two  years, 
while  the  first  pays  for  itself  in  about  one  year.  The 
third  inch  does  not  increase  the  saving  even  in  ten 
years.  The  second  inch,  therefore,  more  than  pays 
for  interest  and  depreciation,  while  the  third  fails 
to  do  this. 

In  the  case  of  the  asbestos  fire  board,  a  second 
inch  in  thickness  causes  a  saving  of  £4  in  ten  years, 
the  third  and  fourth  inches  showing  a  loss. 

166 


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167 


STEAM    PIPES 


In  general  it  may  be  said,  therefore,  that  if  five 
years  is  the  length  of  life  of  a  cover,  one  inch  is  the 
most  economical  thickness,  while  a  cover  which  has 
a  life  of  ten  years  may  to  advantage  be  made  two 
inches  thick. 

In  view  of  the  custom  which  prevails  to  some 
extent  of  wrapping  asbestos  paper  round  a  pipe 
and  surrounding  the  whole  with  hair-felt,  tests 
were  made  as  to  the  temperature  of  the  bounding 
line  of  the  asbestos  paper  and  hair-felt,  using  a 
Le  Chatelier  thermo-electric  pyrometer  for  this  pur- 
pose. The  different  samples  of  asbestos  paper 
give  widely  varying  results,  but  a  general  idea  of 
the  protection  afforded  by  the  paper  may  be  had 
from  Table  F. 

TABLE   F. 

PROTECTION    AFFORDED    BY    ASBESTOS  PAPER.    PIPE  AT    200 
POUNDS  PRESSURE. 


Thickness  of 
Asbestos  Paper. 

Temperature 
of  Pipe. 

Temperature  of 
Inside  of  Hair-Felt. 

Pressure  Correspond- 
ing to  the  Tempera- 
ture of  the  Inside  ot 
the  Hair-Felt. 

^4   inch 

"3T      »> 
1 
TB"      » 

*    „ 

384-7°  Fahr. 

385-0°  „ 
384-6°  „ 

384-7°  ,, 

356°  Fahr. 

329°       » 
302°       „ 
266°       „ 

146  pounds 

102         „ 
7°         M 

39      » 

Attention  being  called  to  the  varying  loss  from 
bare  pipes  when  their  surfaces  were  in  varying  con- 
ditions as  regard  rust,  dirt,  paint,  etc.,  a  few  brief 
tests  to  show  any  large  variation  which  might  occur 

1 68 


SUPERHEATED    STEAM 


from  the  loss  from  bare  pipe,  viz.  13-84  B.Th.U.  per 
square  feet  per  minute,  are  shown  in  Table  G. 

TABLE    G. 

Loss  OF  HEAT  AT  200  LB.   FROM  BARE   PIPE. 


Condition  of  Specimen. 


B.Th.U.  loss  per 
sq.  ft.  per  minute. 


New  pipe          ..... 

Fair  condition  .... 

Rusty  and  black       .... 

Cleaned  with  caustic  potash  inside  and  out 

Painted  dull  white 

Painted  glossy  white 

Cleaned  with  potash  again 

Coated  with  cylinder  oil    . 

Painted  dull  black      .... 

Painted  glossy  black 


11-96 
13-84 
14-20 

I3-85 
14-30 

12-02 
13-84 
I3-QO 
14-40 
12  10 


The  rate  of  heat  loss  from  a  bare  pipe  is  also 
affected  by  the  air  circulation  and  the  temperature 
of  the  surrounding  bodies.  A  few  tests  were  made 
to  indicate  the  magnitude  of  the  errors  likely  to  be 
caused  by  variation  in  these  conditions,  and  a  brief 
examination  of  some  of  the  results  may  be  inter- 
esting. They  are  given  in  Table  H. 

Table  I  shows  the  varying  loss  from  a  bare  pipe 
with  the  change  in  pressure. 

A  very  thorough  test  was  made  of  the  common 
method  of  judging  a  pipe  cover  by  the  sensation 
of  warmth  given  the  hand  on  touching  it,  and 
nothing  too  harsh  can  be  said  of  this  practice.  The 
sensation  is  dependent  to  such  an  extent  upon  the 

169 


STEAM    PIPES 

nature  of  the  surface  that  it  fails  utterly  to  give  any 
idea  of  the  actual  temperature. 


TABLE   H. 

EFFECT  OF  SURROUNDINGS. 


Condition  and  Position  of  Pipe. 


1.  Standard  condition  ;    hung  in  centre  of 

room 

2.  Near  brick  wall,  between  windows   . 

3.  Hung  horizontally  in  centre  of  room 

inches  long 


4.  Vertical  lo-inch  pipejjg  mch 

{. 


lo-inch  diameter  . 
4-inch 
6.  4-inch  diameter  in  draft  from  electric  fan  . 


B.Th.U.  lost  per  sq.ft. 

per  minute  at  200 

pounds. 


13-84 
I4-26 

12-06 

13.48 
14-42 
14-42 
15-20 

20-IO 


TABLE    I. 
VARIATION  OF  HEAT  Loss  WITH  PRESSURE. 


Pressure. 
Lb. 

Bare  Pipe  Loss  B.Th.U.  per  sq.  ft. 
per  Minute. 

340 

15-97 

2OO 

13-84 

IOO 

8-92 

80 

8-04 

60 

7-OO 

40 

574 

The  ease  of  removal  for  repairs  or  alterations 
makes  the  sectional  cover  better  than  plastic  for 
some  work,  but  there  is  much  pipe  surface  which 
might  be  covered  securely  with  plastic,  where  a 
sectional  cover  is  soon  ruined  by  vibration.  Of 
course,  the  plastic  covers  offer  no  possibility  of 

170 


SUPERHEATED    STEAM 


leaky  joints  and  long  cracks.  It  should  be  borne 
in  mind  that  in  most  cases  about  20  per  cent, 
of  the  entire  surface  to  be  covered  is  irregular,  and 
must  be  covered  by  plastic  or  fittings.  It  will  be 
well  for  prospective  purchasers  of  pipe  cover  to  see 
to  it  that  their  contracts  call  for  fittings  and  plastic 
of  as  high  an  efficiency  as  the  sectional  cover  shows. 

TABLE    K. 

MISCELLANEOUS  SUBSTANCES. 


Specimen. 

B.Th.U.  per  sq.  ft. 
per  minute  at  200 
pounds. 

Saving  in  one 
year  per  100 
sq.  ft.  pipe. 

Box  A  : 

i.  With  sand 

3-l8 

£6-92 

2.  With  cork,  powdered  . 

175 

7-88 

3.  With    cork    and  infusorial 

1-90 

778 

earth 

4.  With  sawdust  . 

2-15 

7-58 

5.  With  charcoal  . 

2-OO 

770 

6.  With  ashes 

2-46 

7-38 

Brick  wall  4  inches  thick     . 

5*17 

5-76 

Pine  wood  I  inch  thick  . 

3-56 

676 

Hair-Felt  i  inch  thick  . 

2-51 

7.36 

Cabot's  seaweed  quilt  i  inch  thick. 

278 

7.18 

Spruce  i  inch  thick     . 

3-40 

676 

„         2  inches  thick  . 

2-31 

7-30 

„        3  inches  thick  . 

2-02 

770 

Oak  i  inch  thick  .... 

3-65 

6-62 

Hard  pine  i  inch  thick  . 

372 

6-58 

Eider-down  i  inch  thick  loose 

*r-90  to  270 

— 

„          i    inch    thick   tightly 

*I7O  to  1-80 

— 

packed 

Variable. 


Table  K  gives  some  figures  concerning  a  consider- 
able number  of  samples  of  non-conducting  material, 

171 


STEAM    PIPES 

not,  perhaps,  classed  as  pipe  covers,  but  used  for 
heat  insulation,  which  may  be  of  interest. 

The  box  A,  referred  to  in  the  table,  is  a  f-inch 
pine  box,  large  enough  to  surround  the  pipe,  leaving 
a  one-inch  minimum  space  at  its  four  sides.  In  it 
were  tested  several  materials,  which  are  used  in 
this  way  for  steam  and  cold  storage  insulation. 


172 


CHAPTER    XVI 
Weights   of  Pipe 

THE  weight  of  a  pipe  is  usually  found  by  multi- 
plying the  length  in  feet  by  the  weight  of 
a  foot  length  of  pipe,  and  adding  two  flanges. 
Excellent  tables  of  weights  of  pipes  and  various 
junction  pieces  are  published  by  several  firms  who 
supply  pipes.  For  work  not  using  the  pipes  of 
any  special  maker  the  weight  of  iron  may  be  taken 
as  20  pounds  per  square  foot  for  material  ^-inch 
thick,  and  pro  rota. 

For  steel  pipes  from  |  to  i  inch  thick,  and  from 
10  I.W.G.  to  II.W.G.  the  tables  of  the  Mannesmann 
Company  are  very  full. 

To  calculate  the  weight  of  a  tube  multiply  together 
its  length  in  feet  and  its  mean  diameter  in  inches, 
and  the  number  10-6  x  thickness.  Thus  a  pipe 
6J  external  diameter  and  J-  thick  will  weigh  per 
i  foot  long  6x10-6x0-25.  Approximately,  for 
ordinary  steam  pipes,  10  times  the  external  diameter 
x  thickness  =  weight  per  foot.  Thus  for  a  6J  external 
diameter  pipe  J-  thick  we  have  6-25  x  10  x  0-25  =  15-6. 
The  figure  in  the  Mannesmann  tables  is  15-9.  The 
rule  gives  results  about  2  per  cent,  light  for  small 
thin  pipes  up  to  3  per  cent,  heavy  for  larger  heavy 
pipes,  but  it  is  very  close  to  truth  for  pipes  of 

173 


STEAM    PIPES 


ordinary  use,  and  crosses  the  line  of  plus  and  minus 
error  at  8  inches  external  diameter.  Cast  iron  weighs 
about  6  per  cent,  less  than  steel,  or  9-375  pounds  per 
square  foot  J  inch  thick.  The  following  weights 
per  superficial  foot  I  inch  thick  will  be  useful— 

lb.  lb. 

Cast  Iron  .  .  .  37-50  Copper  .  .  .  46-2 
Wrought  Iron  .  .  40-42  Brass  .  .  .  43-3 

Steel  .         .         .     40-82     Lead  .         .         .59-5 

Thus  wrought  iron  is  I  per  cent,  heavier  than 
the  rule  above  allows  for,  and  steel  is  another  i  per 
cent,  heavier. 

Brazed  copper  tubes  weigh  somewhat  more  than 
solid  drawn.  The  specific  gravity  of  tough  copper 
at  6o°F.  is  8-8917,  or  0-3229  lb.  per  cubic  inch,  or 
practically  3  cubic  inches  to  the  pound. 


Specific 
Gravity. 

Weight  per 
cubic  inch. 

Aluminium        .... 

2-56 

•0926 

Brass,  from        . 

8-82 

•3194 

„    to 

7-82 

-2828 

Gunmetal          .... 

8-70 

•3147 

Copper               .... 

8-69    !      -3146 

,,       drawn 

8-88 

•3212 

„       pipe      . 

8-89 

•3229 

Iron,  Cast         .... 

7-21 

•2607 

,,     wrought  bar 

779 

•2817 

,,     rolled  plate 

770 

-2787 

Lead,  Cast        .... 

ii-35 

•4106 

,,      rolled     .... 

n-39 

-4119 

Nickel               .... 

8-80 

•3183 

Steel  plate        .... 

7-80 

•2823 

Zinc,  rolled      .... 

7-19 

•26OO 

Tin          .... 

7-29 

•2637 

174 


WEIGHTS    OF    PIPE 


Useful  tables  for  the  weight  of  copper  and  iron, 
steel  and  cast-iron  pipes  will  be  found  in  Kempe's 
Year-Book,  or  other  pocket-books  and  manufac- 
turers' catalogues,  and  are  therefore  not  given  here. 

JNO.    SPENCER'S,  LTD.,    STANDARD   DIMENSIONS   OF 
TUBULAR  IRON  &  STEEL  FLANGED  BENDS     (FiG.  60). 


D 

A 

B 

c 

Bore  of 
Pipe. 
Inches. 

Radius  at  Centre. 
Inches. 

Length 
Straight. 
Inches. 

Centre  to 
Flange  Face. 
Inches. 

1 

2 

2i                             41 

1 

2j 

2}                    5 

I 

r     3 

3                       6 

ij 

3! 

3 

6| 

ii 

41 

3 

71 

if 

5i 

31 

2 

6 

31 

91 

21 

. 

en 

71 

4 

"I 

3 

JJ, 

9 

4 

13 

3i 

10} 

5 

4 

12 

5 

17 

41 

r3i 

6 

5 

15 

6 

21 

6 

I   18 

7 

25 

7 

c  1    24^ 

7 

8 

HSJ  |         TT4 
1      28 

8 

3<32 

9 

<!    34 

8 

39! 

10 

o 

40 

9 

49 

ii 

II  " 

44 

9 

53 

12 

< 

I    48 

10 

58 

13 

SJ    58i 

n 

69! 

14 

if" 

63 

n 

74^ 

15 

< 

671 

12 

79i 

16 

Q 

80 

13 

93 

17 

iP~ 

85 

14 

99 

18 

<£ 

90 

14 

104 

19 

ii  Q 

I04i 

15 

119} 

20 

<-s 

no 

16 

126 

175 


STEAM    PIPES 

Bolt  weights  may  be  found  in  any  pocket  book  ; 
sufficient  to  remember  that  a  yard  of  iron  or  steel 
rod  i  inch  square  weighs  10  pounds  per  yard,  and 
7-85  pounds  of  i  inch  diameter,  or  for  any  size,  its 
weight  per  yard  is  D2  x  10  pounds  if  square,  and 
D2  x  7-85  if  round. 


FIG.    60. 


DIMENSIONS  OF  BENDS  (JNO.  SPENCER,  LTD.) 
(Fie.  61.) 


Bore. 

E 

F 

G 

R 

in. 

I 

ft.     in. 
2      O 

ft.     in. 
I      O 

ft.     in. 

o    6 

ft.     in. 

o     3 

2 

3    o 

i     6 

I      O 

o     6 

3 

4    o 

2      O 

i    6 

o     9 

4 

5    o 

26               2O 

I      O 

5 

6    o 

3O               26 

i    3 

6 

7    o 

36               30 

i    6 

7 

8    o 

40               36 

1    9 

8 

9    o 

46               40 

2      O 

9 

IO      O 

5    o 

4    6 

2     3 

10 

II      O 

56           50 

2      6 

ii 

12      O 

60           56 

2    9 

1  To  be  in 

12 

13    o 

66           60 

3     o 

/  3  pieces. 

176 


WEIGHTS    OF    PIPE 


FOR  SOLID  WELDED  &  RIVETED  FLANGES  (FiG.  62) 


B 

D 

N 

a, 

P 

d 

T 

- 

i 

L 

in. 

4 

in. 

9 

6 

in. 

i 

in. 

7i 

in. 
1 

in. 

1 

in. 

in. 

8 

ml 

16 

5 

10} 

8 

i 

8} 

i 

i 

J 

10 

20 

6 

12 

8 

1 

IO 

1 

I 

i 

ii 

22 

7 

13* 

8 

1 

II* 

i 

I 

i 

12 

24 

8 

15 

8 

i 

I2f 

I 

Ii 

A 

13 

26 

9 

16 

10 

1 

I3l 

I 

ii 

14 

28 

10 

17 

10 

i 

i4| 

I 

ii 

T6¥ 

15 

30 

ii 

18 

12 

1 

I 

A 

16 

32 

12 

19 

12 

i 

i6| 

I 

ij 

t 

17 

34 

13 

21 

14 

i 

18 

ij 

Ii 

f 

18 

36 

14 

22 

14 

19 

ij 

if 

i 

19 

38 

15 

23 

16 

20 

l| 

if 

f 

20 

40 

16 

24 

16 

21 

ij 

if 

iV 

21 

42 

17 

25 

r.8 

22 

ii 

if 

TV 

22 

44 

18 

26 

1-8 

23l 

ii 

A 

23 

46 

19 

27 

20 

i 

ii 

i| 

A 

24 

48 

20 

28J 

20 

ij 

26 

ij 

i| 

TV 

25 

50 

21 

30 

20 

i- 

27i 

if 

if 

TV 

26 

52 

22 

2O 

Ti 

28J 

if 

2 

A 

27 

54 

23 

32i 

20 

ij: 

if 

2 

A 

28 

56 

24 

33i 

2O 

ij 

3oi 

if 

2 

29 

58 

j  Dia.  of  Bolt. 


d  Dia.  of  Holes. 


N  No.  of  Holes. 


177 


CHAPTER  XVII 


The   Kinetic  Theory  of  Gases   in   its 
Relation  to  the  Flow   of  Steam 


nnHE  kinetic  theory  of  gases  is  based  on  the 
-•-  assumption  that  the  molecules  composing  a 
gas  are  small  bodies  possessed  of  motion  by  virtue 
of  heat.  All  the  properties  of  gases  are  explicable 
by  this  theory.  Pressure,  for  example,  consists  of 
the  impact  of  the  molecules  on  the  containing 
boundaries  of  the  vessel.  Density  variation  is 
brought  about  by  a  variation  in  the  number  of 
molecules  in  a  given  space.  Pressure  is  varied  by 
adding  or  subtracting  heat,  because,  by  so  doing,  the 
impact  velocity  of  the  molecules  is  made  greater  or 
less.  The  molecules  are  assumed  almost  perfectly 
elastic,  so  that  they  rebound  from  a  surface  at  nearly 
the  velocity  with  which  they  strike  it.  The  mole- 
cules obey  the  first  law  of  motion,  for,  being  in 
motion,  they  continue  to  move  at  the  same  velocity 
in  a  straight  line  unless  acted  upon  by  some  force 
external  to  themselves.  In  any  body  of  gas,  there- 
fore, the  countless  molecules  are  moving  in  ceaseless 
collision  with  each  other  and  the  containing  bound- 
aries, and  the  mean  result  is  a  steady  pressure  and 
temperature  of  the  mass. 

178 


THE   KINETIC  THEORY   OF   GASES 


If  an  opening  be  made  in  the  restraining  boundary, 
the  truth  of  the  hypothesis  is  made  evident,  for  the 
molecules,  which  at  the  time  are  approaching  and 
are  near  to  the  opening,  rush  out  at  once  and  over- 
come the  opposing  molecules  of  the  air  outside,  or 
vice  versa.  The  outrush  or  inrush  continues  until 
a  balance  is  effected.  Until  the  flowing  stream 
falls  to  the  pressure  of  the  surrounding  medium  the 
molecules  will  not  even  tend  to  move  in  parallel 
straight  lines.  There  will  be  transverse  motion  and 
the  stream  will  widen  and  thicken,  or  expand,  until 
the  strength  of  bombardment  of  the  surrounding 
medium  is  equalized. 

When  a  gas  flows  into  a  vacuum  there  are  no 
opposing  molecules  in  front  of  it  to  drive  back,  and 
the  velocity  of  flow  is  obviously  the  inherent  mean 
velocity  of  the  molecules  themselves  at  the  then 
temperature. 

Clausius  calculated  this  velocity  at  o°C.  =32°F.  as 
follows  : — 


Density  =d 

Metres 
per  second. 

Feet 
per  second. 

\ir 

14-5 

485 

I591 

Dxygen 

16 

461 

1513 

lydrogen 

i 

1844 

6050 

Nitrogen 

14 

492 

1618 

steam    .... 

9 

615 

2017 

3arbon  Monoxide    . 

14 

493 

1618 

"arbon  Dioxide 

22 

392 

1286 

The  velocity  in  metres  per  second  is  1844  x 

179 


STEAM    PIPES 

where  d  is  the  density  relative  to  hydrogen,  for 
which  d  =  i. 

The  velocity  varies  inversely  as  the  square  root 
of  the  density,  and  it  varies  proportionately  with 
the  square  root  of  the  absolute  temperature,  as 
naturally  follows  from  Boyle's  law. 

At  o°  Centigrade,  therefore,  the  density  of  steam 
being  9,  its  velocity  will  be  615  metres  per  second  = 
2,017  feet  per  second. 

This  being  the  velocity  of  the  steam-molecule, 
represents  also  the  velocity  of  flow  which  it  tends  to 
achieve  into  a  perfect  vacuum.  Excepting  so  far 
as  pressure  -in  the  case  of  saturated  steam  has  its 
own  particular  temperature,  the  pressure  of  a  gas 
is  no  measure  of  its  molecular  velocity.  We  can 
therefore  calculate  the  velocity  of  flow  of  steam  into 
a  vacuum  if  we  know  its  temperature,  and  the 
following  table  shows  the  results  calculated  for  a 
few  cases  from  the  datum  615  metres  per  second 
at  o°C. 

Experiment  has  shown  that  steam  flowing  from 
one  pressure  to  another  not  greater  than  58  per 
cent,  of  the  initial  pressure,  attains  a  maximum  of 

flow  whence  is  deduced  a  rule  that  W  = —    where 

7 

W  =  weight  of  flow  per  minute  in  pounds. 
P  =  absolute  pressure  in  pounds. 
A  =  area  of  orifice  in  square  inches. 

Calculated  out  for  100  Ib.  absolute  pressure,  the 
outflow  per  second  through  an  area  of  one  square 

180 


THE   KINETIC  THEORY  OF   GASES 


Pressure. 
Absolute. 

Temperature. 

Absolute  Temperature. 

Velocity. 

Ib. 

C° 

F° 

C° 

F° 

Metres 

Feet 

per  sec. 

per  sec. 

0'207 

12-34 

54*21 

285-34 

5I3-2I 

629 

2064 

0-453 

24-89 

76-80 

297-89 

535-80 

642 

2106 

0-698 

32-35 

90-24 

305-35 

549-24 

649 

2129 

0-944 

3778 

100-05 

31078 

559-05 

656 

2152 

1-189 

42-13 

107-84 

3I5-I3 

566-84 

660 

2165 

1-435 

45'74 

H4-34 

31874 

573*34 

664 

2179 

i  -680 

48-85 

119-94 

32I-85 

578-94 

667 

2188 

1-926 

5I-59 

124-89 

324-59 

583-89 

670 

2198 

2-172 

54-06 

129-31 

327-06 

588-31 

673 

2208 

2-427 

56-28 

133-32 

329-28 

592-32 

675 

2214 

4-873 

71-80 

161-25 

344-80 

620-25 

69I 

2267 

5-856 

76-14 

169-07 

349-H 

628-07 

695 

2280 

6-838 

79*92 

I75-87 

352-92 

634-87 

699 

2293 

14-697 

100-0      212-00 

373-00 

671-00 

718 

2356 

50-000 

138-3      280-90 

411-30 

739-90 

755 

2477 

lOO'OO 

164-2      327^3 

437*20 

786-63 

778 

2553 

150-00 

181-2     358*22 

454-20 

817-22 

793 

2602 

200-00 

194-20    381-64 

467*20 

840-64 

800 

2625 

250-00 

203-00   401-10 

476-00 

860-10    812 

2664 

300-00 

214-14   417-50 

487-14 

876-50    821 

2694 

— 

260-0  :  500-00 

533-oo 

959-00 

859 

2818 



315-5    6oo"oo 

588-55 

1059-00 

903 

2961 

foot  would  be  2057  pounds,  whereas  the  tabular 
number  2,553  cubic  feet  reduced  to  pounds  gives 
586-4  as  the  weight  that  should  apparently  pass  by 
the  kinetic  theory.  The  discrepancy  probably  arises 
because  molecules  of  an  enclosed  gas  are  moving  in 
every  direction  relative  to  an  orifice  in  the  wall  of 
the  vessel,  and  those  molecules  travelling  straight 
for  the  outlet  are  hindered  by  those  moving  along 
the  other  two  space  dimensions.  To  pass  a  full 
quantity  through  an  opening,  the  approach  to  that 
opening  should  be  of  the  correct  tapering  form  and 
so  should  also  be  the  outlet  end.  The  effect  is,  in 

181 


STEAM    PIPES 

fact,  simply  the  commonly  recognized  vena  con- 
tracta  effect.  But  as  much  steam  will  flow  into  a 
pressure  of  one-half  the  initial  pressure  as  into  a 
vacuum. 

If  it  were  possible  to  persuade  all  the  molecules 
of  a  flowing  jet  of  steam  to  move  together  in  parallel 
lines  then  by  directing  the  stream  upon  the  suitably 
shaped  vanes  of  a  turbine  moving  at  a  velocity  one- 
half  that  of  the  steam,  the  steam  molecules  would 
drop  from  the  turbine  deprived  of  all  energy,  or 
movement,  or  heat,  and  the  efficiency  of  the  turbine 

would  be  100  per  cent.     We  know  that  a  heat  engine 

y y 

cannot  have  an  efficiency  of  more  than  E=^= — 2 

*  i 
where  T^  and  T2  are  the  upper  and  lower  absolute 

temperatures,  and  that  the  assumed  molecular 
movement  is  not  possible,  but  this  idea  is  at  the 
bottom  of  the  steam  turbine,  in  which  the  action 
of  the  steam  is  obtained  by  allowing  its  molecular 
kinetic  energy  to  manifest  itself  as  mechanical 
kinetic  energy — a  distinction  without  a  difference, 
for  all  steam  energy  is  really  kinetic. 

Though  the  mean  molecular  velocity  of  steam 
may  fall  short  of  3,000  ft.  per  second  in  all  practical 
cases,  certain  writers  refer  to  a  possible  outflow 
velocity  as  high  as  5,000  ft.  per  second.  Apparently 
this  velocity  could  only  occur  where  the  flowing 
molecules  were  assisted  by  the  energy  of  those 
behind,  which  wTould  be  much  cooled  by  the  opera- 
tion, losing  as  much  velocity  as  the  outgoing  mole- 
cules had  gained  over  and  above  the  mean  value. 

182 


THE   KINETIC  THEORY   OF   GASES 

This  hardly  seems  possible,  and  velocities  above 
those  in  the  table  seem  hardly  probable. 

Those  who  are  interested  in  the  subject  cannot 
do  better  than  study  Meyer's  work  on  the  Kinetic 
Theory  of  Gases.1 

The  theory  is  certainly  an  aid  in  the  comprehen- 
sion of  the  behaviour  of  flowing  steam,  and  if  clearly 
grasped,  it  will  help  to  explain  why  the  efficiency 
of  a  heat  engine  is  so  small. 

1  The  Kinetic  Theory  of  Gases,  by  O.  E.  Meyer.  Translated  by 
Robert  Eaynes,  M.A.  Longmans  and  Co. 


183 


APPENDIX 

AT  the  moment  of  going  to  press  the  Standards  Committee 
have  issued  their  long-delayed  report  on  pipe  flanges. 
Standards  are  fixed  for  the  flanges  of  all  pipes  and  fittings  from 
J  in.  to  24  ins.  in  steps  of  J  in.  up  to  2  in.  diameter  ;  of  J  in.  from 
2  in.  to  5  in.  diameter,  and  for  four  series  of  pipes,  low  pressure 
intermediate  high  and  extra  high,  or  for  steam  pressures  up  to 
55  lb.,  125  lb.,  225  lb.,  and  325  Ib. 

The  diameters  of  flanges  and  bolt  circles  and  the  number  of, 
bolts  are  the  same  for  all  pipes  of  the  same  bore,  save  for  the 
low-pressure  series,  for  which  the  diameters  of  flanges  and  bolt 
circles  are  that  of  the  next  size  smaller  of  the  high-pressure  series. 
Flange  thickness  and  bolt  diameter  increase  with  increase  of 
pressure.  The  number  of  bolts  is  always  a  multiple  of  4,  and 
bolt  holes  straddle  the  centre  lines  as  recommended  by  the 
author. 

For  long  lines  of  pipes  with  welded  flanges-  the  diameter  of 
flange  is  the  same  as  that  of  the  next  size  smaller  cast  iron-pipe. 


INDEX 


Admiralty  practice  with  cop- 

per,  34 

Alloy,  steel,  44 
Aluminium,  174 
American  pipe  list,  48 
American  standard  flanges,  144 
American  threads,  38 
Anchoring,  67,  92 
Anti-priming  pipes,  76 
Arrangements,  general,  105 
Asbestos  paper,  168 
Atmospheric  valves,  147 

B 

Babcock  &  Wilcox  Co.,  141 
Bending  pipes,  98,  103 
Bends,  27,  32,  175 

—  expansion,  56 
Board  of  Trade  rules,  74 
B.E.T.,  Co.  138 

Boiler  output,  no 

—  position,  106 
Bolts,  140,  175 
Brackets,  88,  92 
Branches,  65,  136 
Brass,  174 

Bursting  pressure,  54 
Bye -pass,  117 


Cast  iron,  23 

Copper,  23,  32,  35,  84,  174 

Cork  coverings,  160,  166 

Coverings,  153 

Crane  Co.,  142 

Crosses,  26,  133 


Danger  of  galleries,  119 
—  spigots,  83 
Dashpots,  150 
D'Aubisson's  experiments,  7 
Dimensions  of  junctions,  28 
Double  seat  valves,  125 
Drainage,  128 


Economy,  108 

—  of  small  valves,  109 
Elasticity,  81 
Elbows,  133 
Erection,  97 
Exhaust  heads,  145 

—  valves,  125 
Expansion,  52,  55 

—  bands,  56 

—  co-efficients,  67 

—  joints,  59,  63 

—  of  boiler  seat,  69 

—  traps,  129 
Extension  saddle,  101 


Ferranti  on  pipes,  34 
Flanged  bends,  175 

—  joints,  83 

Flanges  38,  40,  43,  83,  133, 

137.  J77 

Flexible  pipes,  35, 47 

—  seats,  125 
Flow  of  steam,  4,  12 

—  Babcock  &  Wilcox  rule,  1 1 

—  Geipel's  rules,  18 

—  practical  rules,  10 


185 


INDEX 


Flow   of  Steam,    Stromeyer's 

rule,  10 
—  Kinetic  theory  oi,  178 


Gallery  for  valves,  119 
Gases,  kinetic  theory  of,  178 
Geipel's  rules  for  flow,  18 
General  arrangements,  105 
Gun  metal,  174 

H 

Hair  felt,  154,  165 
Hangers,  88 

Barter's  swivel  joint,  63 
Hutton's  rules,  10 

I 

Iron,  cast,  174 

—  rolled,  174 

—  wrought,  174 
Isolating  valve,  123 

J 

Joints,  41,  51,  63,  83,  85 

—  expansion,  59 

—  flanged,  83 

—  for  superheater,  41 

—  Harter's,  63 

—  socketed,  45 

—  spigot,  83 

—  swivelling,  63 

—  taper,  99 

—  telescopic,  62 
Junction  pieces,  26,  133 

K 

Kinetic  theory  of  gases,  178 

L 


Lead,  174 


M 


Manganese  steel,  140 
Materials,  23 
Molecular  velocity,  178 

N 

Nickel,  174 
Non-return  valve,  80 
Norton's  tests,  156 

O 

Outlet  valves,  78 


Pipe  bending,  103 

—  coverings,  153 

—  general  principles,  2 

—  joints,  41,  51,  83 

—  ratios,  17 

—  strength,  54,  72 

—  supports,  88 

—  thickness,  24,  50,  53 

—  threads,  38,  49 

—  weight,  173 
Practical  rules,  10 

R 

Rankine's  formula  for  flow,  5, 

14 

Radius  of  bends,  32 
Ratio  of  pipes,  17 
Resistance  to  flow,  13 

—  of  openings,  21 
Ring  Main,  105  109, 

—  joints,  85 
Riveted  pipes,  39,  73 
Rollers,  94 
Rubbing  pieces,  92 
Rules  for  pipes,  10 
Russell,  James,  &  Sons,  143 


Magnesia,  159 
Mains,  105 
Making-up  lengths,  97 


Saddle,  extension,  101 
Saving  by  pipe  covers,  161 
Separators,  145 
Slag  wool,  155 

186 


INDEX 


Slide  valves,  79 
Sliding  pipe  joints,  62 
Socketed  joints,  45 
Spencer,  John,  Ltd.,  on  pipes, 

49 
Spigot  joint,  danger  of,  83 

Steam  flow,  4,  12,  178 

—  pipes,  i,  2,  3 

—  traps,  129 
Steel,  23,  36,  174 

—  alloy,  44 

—  manganese,  140 
Stock  lengths,  54 
Strength  of  copper,  33 

—  pipes,  72 

—  wrought  iron,  72 
Stromeyer's  rule  for  flow,  10 
Superheater,  41,  84,  106 
Superheated     steam,     7,     86, 

152 

Supports,  88 
Suspended  pipes,  91 
Swivel  joint,  Harter's,  63 


Taper  joint  rings  99 
Tees,  26,  133,  177 
Telescope  pipe  joints,  62 
Templets,  98 

Tenacity  of  metals,  34,  72 
Thickness  of  pipes,  24 
Threads,  pipe,  48,  49 
Tin,  174 
Traps,  129 


Valves,  112 

—  angle,  112 

—  bye-pass,  116 

—  double  seats,  126 

—  economy  of  small,  105 

—  exhaust,  124 

—  flexible  seats,  125 

—  fullway,  116 

—  isolating,  80,  123 

—  non-return,  80,  123 

—  outlet,  76,  78,  112 

—  position,  119 

—  reversed,  120 

—  slide,  79 

—  straightway,  114 
Velocity  of  flow,  4, 178 
Vena  contracta,  21,  178 
Vibration,  67,  91 

W 

Waste  of  capital,  109 

Water  hammer,  81 

Weight  of  junction  pieces,  134 

—  pipes,  173 

—  materials,  174 
Whitworth  threads,  49,  73,  74 
Wrought  iron,  23, 36 


Y-pieces,  133 


Zinc,  174 


OF   THE 

UNIVERSITY 

OF 


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